League of Legends : Teemo Town: Teemo AP build

This is an excellent guide that I found at LeagueCraft.com for an AP Teemo build. This guide changed the way that I play Teemo, and it changed it for the best. Everything in this guide is useful, even if you're not into playing Teemo as AP, or Teemo at all. Direct link to the guide here: LINK

Introduction

The guide is up to date as of 2012-1-10.

Hi,
I am AnjouShin. I play Teemo since late open beta and I have accumulated over 800 games with him by now.
I have yet to grow tired of playing him.
Please believe me that I know what I am talking about when I suggest something.
Solo-Queue also proves to be hard at times so I recommend you play with at least one friend.
Once you master him you know why AP Teemo is the way Teemo has to be played.
You can find alternative builds (including the one Rainman uses) in a seperate section.
Check the video section if you want to see some of Teemos unique skills.

Have fun while trying my Teemo and never underestimate the power of the scout's code.
(the Goblin Techies will be proud of you)

here are some pictures of me

Abilities

This is a nice passive and helps you to hide from enemies or to initiate fights sometimes.
It is by far not as useful as real stealth champion's since you can be knocked out of stealth by many things like knock-ups or blitz' pull.
It can help you defending turrets by going stealth and opening an assault with blind dart and 2 toxic shots.

Don't rely on it and think of it as little more than an extra.

This is your main damage nuke and a very good counter to DPS carries with the blind and the good scaling.
Its also your main means of triggering your late game.
It resets your autoattack timer which means that you can hit the enemy 3 times within a very short time span.
(you can see it in the video on different occasions and its especially helpful in the dfg, dart, toxic shot/lich bane combo)

A very helpful skill that makes you stay alive and chase people with unmatched speed while being a passive. With basic boots you are almost as fast as a melee champion with improved boots. With improved boots you can outrun someone with improved boots and ghost. The active component adds some survivability and should not be underestimated.

Your tertiary means of triggering your late game. (mainly during chases, use Move quick for what it was intended)

Early game this skill is used to make last hitting easier and to harass the enemy. It makes towerdiving hard and should not be applied when you want to suppress someone and get a few shots at the tower.early-mid game it increases your DPS, especially in combination with . Late game it deals a large amount of damage since it scales 1:0.7 if you get the full duration poison.
Stacking attackspeed is a bad idea since only the in-build burst is added each hit and every second of poison scales equally.

e.g. Lvl 5 posion deals 45(+100) magic damage on hit and 30(+100) damage each second for 4 seconds. That means stacking attackspeed only leads to an increase of 15 magic damage on hit. (which means you have over 715AP)

Some people say this is the skill that makes AP Teemo viable. While it is a great mine that deals a lot of damage it still can be countered and you cannot use it teamfights like an instant damage nuke like so many others can. Without the mushrooms Teemo is still 70-80% combat effective.
Do not use mushrooms to farm minions except late game when you have to farm one huge creep wave.

Your secondary means of triggering your late game.

Quick overview

If you are impatient with the attention span of a fly or your game is about to start this is what you are looking for.

Summoners Rift

Pregame:
9 x magic pen
9 x HP/lvl
9 x MR/lvl
3 x flat AP or  3 x magic pen
21/0/9 with Exhaust and Flash

Ingame:
Items:

Abilities at lvl 6:
2x, 1x, 2x, 1x

Crystal Scar

Pregame:
9 x magic pen
9 x armor/lvl or     9 x health/lvl
9 x MR/lvl or     9 x CDR/lvl
3 x Magic pen
9/0/21 with Exhaust and Ghost

Ingame:
Items:
Refinery/Drill

Windmill

Abilities at lvl 4:
1x, 1x, 2x
Pros / Cons

Pros:

+ easy to last hit during lane phase
+ very fast movement speed (highest average movement speed in the game)
+ good scout
+ good nukes
+ long blind (the only reliable blind in the game)
+ free reconnaissance mines
+ high resistance to junglers
+ easy last hitting minions in early game
+ high DPS mid game
+ high nuke potential late game
+ changes roles during the game according to the requirements of the game phases
+ great against most champions mid lane
+ strong in side lane

Cons:

- low HP early and early-mid game
- oracles elixir can counter him to a certain degree
- the games might take a very long time (sometimes over 60 minutes) because the enemy is too afraid to go somewhere
--> long sieges possible at the enemy inhibitor turrets
- you get focused a lot
- you cannot initiate well unless they hit a mushroom or you can pick off stragglers
- every time you see a fail Teemo in your team you want to cry
Runes and Masteries

There is no special trick or awesomeness in the runes and masteries you need.

Summoners Rift

Runes:
Greater Mark of Insight x 9 (magic pen)
Greater Seal of Vitality x 9 (hp/lvl)
Greater Glyph of Shielding x 9 (MR/lvl)
Greater Quintessence of Potency x 3 (flat AP) or  Greater Quintessence of Insight x 3 (magic pen)

magic pen vs ap is a matter of personal choice here. basically you trade mid-game dps for early game damage when you exchange magic pen quints for ap quints. it helps you fight people like Malzahar or Brand very effectively lvl 1-5.

Crystal Scar

Greater Mark of Insight 9 x magic pen
Greater Seal of Defense 9 x armor/lvl or     9 x health/lvl
Greater Glyph of Shielding 9 x MR/lvl or     9 x CDR/lvl
Greater Quintessence of Insight 3 x Magic pen

Masteries:

a basic 21/0/9 mastery tree for Summoners Rift

and 21/9/0 for Crystal Scar
Summoner Abilities

My advice for Teemo's Summoner Abilities is:

Exhaust and  Flash and  Ghost for Crystal Scar

"Wait? Exhaust? Why? He has a blind already! Why would you need a damage reducing spell as well?"
Exhaust is one of the most versatile Summoner spell in the game. It reduces the enemy damage and slows for 2.5 seconds.
If you go for Summoner's Wrath it lowers the armor and magic resist by 10. (see also: Runes and Masteries).
It can be used to reduce caster damage as well (Karthus, Nunu, towerdiving Vlads you get the idea)

Flash is a pretty straightforward skill. It helps you to get away from our enemies as well as being a great repositioning tool during fights whatever their scale is. Should you get chased down you can Flash and Move Quick
out of most situations. They can't stun you when you are out of range =)
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if you hate flash (or its being removed) you can go for
Exhaust  Ghost
keep in mind that the Move Quick active is a little ghost for 4 seconds that should provide more survivability in combination with flash then ghost with the active.
Don't use ghost and move quick at the same time but move quick first and then ghost. Otherwise you will get only 50% for both abilities due to a 50% reduction after hitting a certain movespeed value. If you use move quick first there is a good chance you can save your ghost or if you need ghost still you have ghost 4s longer than your enemy.
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another possible setup:
Surge  Flash
You will miss the damage reduction of 35% against casters (which is mainly why you are going for it) but with Cleanse being able to get rid of exhaust it is a viable combat buff to outdamage your enemies over a longer period of time than only 2.5 s. high nukes will be a problem but most of them (e.g. [spell_text=summon tibbers], Nether Grasp, Sigil of Silence) will outrange exhaust anyway and act as an initiator.
This setup needs further testing!
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I do not advise going for:

Ignite
You have a DOT with your autoattack that hits harder, the heal reduction is missed at times (especially against some corporation employees and several barbarian kings) but there is always someone with ignite on your team to do the job.
Know when to engage and how to kill and you will never need ignite to finish somebody off.
"Get ignite for first blood!"
Congratulations, you just gimped you for the entire game so you MIGHT get 100 gold extra.

Teleport
you move around the map fast enough with move quick. Teleport to mushrooms is overrated the cooldown is too long and it brings no utility or damage for teamfights. The benefits is brings are easily canceled out by the damage you deal to your own teamfight capabilities.

Clarity
with the runes and masteries you should have close to no mana problems. It is also a waste of a summoner spell after level 9 (or after you got your P-Stone see items).

Clairvoyance
good spell on certain characters but a bad choice on Teemo. Your mushrooms should provide enough vision to reveal incoming ganks. If they simply evade every single mushroom's LOS (line of sight) you are better of with a damage reduction/slow or a repositioning tool than a vision spell. Its better suited for support champions than on AP scout assassins.
If the side lanes don't buy wards for only 37.5g per player it is not your fault should they overextend and be ganked.
If you see they have a jungler/mia and your lanes are overextended tell them something like: "care top ww!" or "mid going top" etc.

the other summoner spells should not even be considered.
Skilling Order

The skilling order greatly depends on who you face.

Fighting a mage or a high HP/high regen tank (cho'gath, mundo, garen, mordekaiser) go for Toxic Shot as your level 1 ability. (also if you go for a 2v1 or 2v2 lane)

When fighting a DPS (or any sort of enemy Teemo) you need Blinding Dart as your first ability. This way you have a good nuke with a blind that might save you live should you fail and overextend too early.
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Upgrade both abilities roughly to the same degree. even if you don't need to blind veigar mid you can still be ganked so get a few points in your dart. If you level up blinding dart too fast you will run out of mana.

At level 3 (especially if you don't have boots at lvl 1), 4 or 5 (only if you don't have to dodge and the enemy has no roamer/jungler) you get one point in Move Quick and upgrade it further after level 13 (once blind dart and toxic shot are at lvl 5)

your level 6 should look like this (except for very few exceptions):

2x Blinding Dart
1x Move Quick
2x Toxic Shot
1x Noxious Trap
Items

The right build is, as usual, the key to success or defeat.

Summoners Rift:

Regrowth Pendant and one Health Potion or  Boots of Speed and 3x Health Potion
are your first items. They make you stay in lane for a very long time. (sometimes up to 15 minutes and about 2500 gold).
next items are (in that order usually)
Philosopher's Stone
Boots of Speed
Kage's Lucky Pick
Mejai's Soulstealer
Malady starting with Dagger
Rod of Ages starting with Ruby Crystal
Sorcerer's Shoes
Deathfire Grasp
sell your Philosopher's Stone*
Rabadon's Deathcap starting with Needlessly Large Rod
sell  Malady and build  Lich Bane(most likely) or  Void Staff(very rare)
(see also role rotation principle)

*you can sell the Philosopher's Stone straight if you want but you can turn it into an Eleisa's Miracle and then sell it immediately to get an additional 10g which can help if you are waiting for a tiny bit of gold to buy the Needlessly Large Rod (thx to Magix for pointing that out).

Note: there is no CORE build for this Teemo since every item (excluding Mejai's Soulstealer) changes Teemos role in the game (see 'Role rotation principle' right below this section).

experimental late-late game build: (I had to use it only one time during a very long game)

Deathfire Grasp
Rod of Ages
Rabadon's Deathcap
Lich Bane
Void Staff
Mercury's Treads or  Boots of Swiftness
Elixir of Brilliance

You lose a lot of AP but if you can't keep your Mejai's stacks that late anyway it's worth to consider the change in items.
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Crystal Scar:

the most effective build i have found so far is this:
NOTE: the items are quite interchangeable on Crystal Scar so you might want to get an early Lich Bane if your movement speed is too low or you need the extra nuke, an early Hextech Sweeper against a stealth heavy team or an early Rabadon's Deathcap if you cannot get very close.

AP scout
Prospector's Ring and  Boots of Speed when going for the Windmill
Blasting Wand and  Amplifying Tome when going for the Refinery/Drill
Sorcerer's Shoes
Malady
Fiendish Codex
Needlessly Large Rod
Deathfire Grasp
Rabadon's Deathcap
Lich Bane
Hextech Sweeper(cause of your poison and mushrooms increase the vision on it even more up to 9 seconds)

Tanky Dps on-hit hybrid
[item=prospector's blade]
Boots of Speed
Kitae's Bloodrazor
Mercury's Treads
Malady
Entropy
Odyn's Veil
Guardian Angel
this build works but Teemo's autoattack range is just too low to be very effective

Twisted Treeline:
Video section

The Video showing some Unique Skills of Teemo with this build

if the embedded vid isnt working try this link.

here is a full game with my build divided into 2 parts (I have to admit that there is some weak last hitting early).
Role rotation principle

Unlike other champions Teemo does not follow the same role during the game but follows different roles according to the requirements of the different phases of the game. A Tank tanks and provides CC, a bruiser provides soft taunt, a DPS attacks everything as long as possible etc.
With the build described above you go through several roles suited for the characteristics of each phase.

the game starts.
- lane staying
- farming
- holding mid
- securing mid
- helping to gank enemy junglers
--> farming teemo

you buy a  Regrowth Pendant and a  Health Potion as your first items.

the game continues until you have 1940 gold. (13 minutes-ish without kills).

recall and buy
Philosopher's Stone
Boots of Speed
Mejai's Soulstealer

early-mid game starts.
- quick ganks
- short teamfights with 3-5 players
- defending or killing dragon
- pushing towers over a longer period of time
- securing mid
--> ganking teemo

run back to the front. place more shrooms and start to gank people if necessary and/or possible.

after you buy your Malady
late mid-game starts
- ganks
- short teamfights with 4-7 players
- defending or killing dragon
- pushing towers over a shorter period of time
- securing mid if needed
- creep wave management becomes important
--> on-hit DPS Teemo

now you are pretty much a glass cannon. good you brought
Rush your . (about 25 minutes if you killed stuff and farmed well, up to 32 minutes if you didn't. sell your philosophers stone if you have to to get it before 35 minutes). Malady enables you to push towers effectively.

early late-game starts.
- teamfights with 6-10 players
- MR and armor on tanks start to get over 175
- creep wave management becomes very important
- securing Baron Nashor
- warding and shrooming the enemy jungle becomes more dangerous
--> fighting DPS Teemo

You stop being a glass cannon and can take a beating in a fight, Teemo Taunt (see video section) starts to be effective.
Sorcerer's Shoes come as you play. Mushrooms start to hurt a lot.

you continue with your one of your most deadly weapons:
Deathfire Grasp
late late-game starts.
- Teamfights with 8-10 players
- violent tower pushes
- you get focused hard
- securing Baron Nashor
- longer teamfights
- dps carries start to shine
--> nuke and dps mage Teemo

Your damage shifted massively from on-hit + base-AD to almost pure magic damage (the base damage is reduced by base armor of your enemies).
Blind dart and toxic shot deal a LOT of damage.
The  Rabadon's Deathcap comes as you play. Start it with a  Needlessly Large Rod (1200 gold + 390 gold from turning the Philosopher's Stone into  Eleisa's Miracle and immediately selling it afterwards for 10g extra, which really helps if you are waiting for 20g more to buy your NLR)

end-game starts.
- heavy focus
- killing Baron Nashor
- violent long teamfights
- sieges at turrets and inhibitors
--> heavy nuke Teemo
(one of my enemies called me Drive-by-Teemo once which sums it up pretty well actually)
to decide what your last item is you need to ask yourself:

Is the enemy team focusing me? (aka business as usual)  Lich Bane

your nuke potential is increased massively. you simply blast your way to victory while running away from everything that tries to kill you (watch out for  for the sake of your move quick). Excellent siege breaker (over 1000 damage to inhibitors in one shot). MR, movement speed, decent AP on top of it.

The enemy has at least 3 banshees and has not surrendered yet?  Void Staff

Pretty simple: average AP and 49% magic penetration. still the worst choice of the 2 but sometimes your only way to deal damage. This usually happens when you do not have enough DPS on your team (e.g. Morgana, Kennen, Mordekaiser, Teemo, Akali) so it can be avoided in champion select.

IF the game continues after this AND you have trouble keeping your stacks:

Sell Mejai's Soulstealer and buy either the Void Staff or the Lich Bane whichever you haven't. Don't forget to keep your Elixir of Brilliance active to retain the 39% CDR.
Change your Sorcerer's Shoes for Mercury's Treads after.

Potion and "I have 3k gold extra... why didn't we win already?" phase starts
Item and Build analysis

Okay here are some items analyzed on how to use them and why you want them. Some items might be considered unfitting or simply bad items. Also the question on about CDR on Teemo and its uses is answered here (Nashor's Tooth).

Philosopher's Stone
Question:
Are you mad? Why no Ruby Crystal... you have no HP!?! Why no Meki Pendant? Why no Doran\'s Ring?

Deathfire Grasp and Malady
Question:
Do you use 4 shots with Malady before you use your Deathfire Grasp or do you use the Deathfire straight without the MR reduction?

Question:
Deathfire Grasp Who to use it on?

Rod of Ages(ROA)
Question:
Why that late in the game? ROA before 15 minutes or never.

Rylai's Crystal Scepter vs. Rod of Ages
Question:
Which one is better?

Nashor's Tooth and CDR
Question:
Why no Nashors? You need no CDR? You need no attackspeed? Are you a noob?

Mejai's Soulstealer
Question:
I can't keep the stacks. How can I replace it and when?

Hextech Gunblade
Question:
Why not? Spellvamp, slow, AD, AP, lifesteal?

Guinsoo's Rageblade
Question:
Tons of AP, AD, AS for only 2235g... why not?
Hybrid, DPS, on-hit builds overview

the following build is viable in high ELO play though its quite boring to use

tanky-on-hit-dps-hybrid:
(thats the one Rainman uses)

Runes, Summoner abilites, Masteries:

Greater Mark of Desolation x 9
Greater Seal of Vitality x 9
Greater Glyph of Warding x 9
Greater Quintessence of Fortitude x 3 or  Greater Quintessence of Potency

21/9/0
with both 10% penetration masteries and veterans scars, no crit chance or damage

Ignite  Flash

Items: (based on rainmans guide)

Starting choices:
Doran\'s Blade (up to 3 of them) if you get early jungle pressure
Boots of Speed and  Health Potion against matchups that are likely to outplay you or that require mobility
Cloth Armor and  Health Potion against physical harass like GP or Panth

Core:
Wriggle's Lantern
Phage  (if you get it early enough you can skip the Doran\'s Blades)
Mercury's Treads

Late game:
Frozen Mallet
Madred's Bloodrazor
Guardian Angel

Viable in high ELO play. quite boring to use unless you like to right click a lot. spells provide little more than utility, toxic shot and move quick leveled first since blind dart is only used for utility. mushrooms for supporting wards, slowing enemies and securing the lane. basically turns teemo in a hybrid damage tanky dps. used for split pushing and lane control. Victory through strategy and actively avoiding teamfights.

I still have to run into any trouble facing a Teemo using this build against my Teemo =(

the following builds are for fun. AD/AS Teemo is not viable. Hybrid is not great. AP is the way to go but if you are looking for quick fun in a practice game or if your team is really strong anyway you can try one of these:

Hybrid:

DPS(physical damage per second):
Advanced solo tactics list (alphabetically sorted)

So these are my experiences with a LOT of 1v1 fights. Some champions I never played against in mid after my hundreds of solo-mid AP-Teemo games are found here:(also incudes champions that are so easy to fight against that further explainations are a waste of time to write and read):

Alistar, Amumu, Blitzcrank, Evelynn, Garen, Irelia, Janna, Jarvan IV, Jax, Kayle, Leona, Malphite, Maokai, Mundo, Master Yi, Nassus, Nocturne, Olaf, Poppy, Rammus, Riven, Shaco, Shen, Shyvana, Singed, Sona, Soraka, Taric, Teemo (once you play him a bit you know his weaknesses), Trundle, Tryndamere, Udyr, Warwick, Xin Zhao

Remember this is no direct 1v1 fight and no teamfight. Its just during the 1v1 lane phase. I base this on very few early-mid game items from Regrowth Pendant and Health Potion up to Philosopher's Stone, basic boots, Mejai's Soulstealer and maybe a Dagger.
use Ctrl+F to search for a champion you want to know about.
okay here are the ones that really need some thought (or can be found mid more than once ever 100 games).
(Unkillable does NOT mean that he cannot be killed, it means that it is very hard to kill the champion on your own. it does not mean that he can kill you back as well)

Click here to open the list
Dual Lane tactics

So you have played a few games dominated mid over and over again and you want to do it again.
You call "AP Teemo mid" in champ select don't log in and wait for the 80s to be over. The Vladimir switches to Ashe in the last 2 seconds.
The game starts.

You buy your regrowth & H-potion and check if you really selected the right rune page. You run down mid.

1E37h4X0R(Ashe): im mid biatches!
Boscogn(Teemo): i called mid in champ select
1E37h4X0R(Ashe): lol teemo mid
1E37h4X0R(Ashe): go home scrub! im a better dps than you
1E37h4X0R(Ashe): bro
1E37h4X0R(Ashe): bro
1E37h4X0R(Ashe): brO!
Boscogn(Teemo): you didnt even buy any items
1E37h4X0R(Ashe): i need the gold for mah early bf sword
IdrinkMilk(Poppy): let Teemo mid... he called it in champ select
Boscogn(Teemo): yeh come on
Boscogn(Teemo): dont be an idiot
1E37h4X0R(Ashe): /ignore team
1E37h4X0R(Ashe): bro

there is no way you're going to get mid from people like that. they rather go 2v1 mid than playing the game. Even if you have 3 friends with you supporting the awesome teemo mid... forget about it. maybe you can steal mid from him after he gave first blood or something.
If someone insists on mid you might be able to convince them by simply sitting in mid till someone leaves(before you guys gimp each others exp though... never steal exp from the mid early!).

so you end up in a side lane. what do you do?

Get Toxic Shot first. it deals half of your blind dart as damage and considering you need about 2 minion waves + 1 minion to reach lvl 2 you can deal a lot more dmg with it, farm better and conserve mana.

Two stun combo enemies(and other heavy CC):

the most prominent combo is Taric-Sion here. Others are Morgana/Lux with maybe Renekton/Annie, Nunu with Ryze, Zilean + Xin Zhao.
These is the most dangerous combo you can face in a 2v2 side lane (not to mention 2v1 top).
You need to last hit only and you wont be able to do much till lvl 6 and you can place a mushroom in the bush to scout.
Focus on leveling your Toxic Shot first and get move quick early.
Sometimes you need to let them waste their stuns on you by running forward and the Move Quick back into your turret.
The biggest problem of heavy CC is that it is extremely mana consuming especially early in the game. (Sion 100 mana cost in from a 240 mana pool).
You need to shroom the bushes heavily. 3 per side bush and 1 in river bush should be enough(risk to be ganked very low cause you can't really leave the turret.)

Watch out for Clarity and Ignite.

Good thing is that if you last hit only can can keep up in exp and minion kills while making them overextended.

Your Teammate Mr. Coward:

This is frustrating but not that bad. He will towerhug and is too afraid to engage. He will start fighting once you reached lvl 6 and started to shroom a bit so he can be safe. Sometimes a "if you tank them I can kill Zilean" helps.
Shroom balanced but place a few more shrooms near your turret. 2 per side bush and 2 for river bush and the area around it (risk to be ganked relatively low).

Sure a shen with 1200 HP running from a 900 Hp Sivir is weird to look at but at least he is not pushing like...

Your Teammate Mr. Irrational:

Those are the guys you hate. They run from a balanced fight just to jump back in once the battle is over. They will push like a mad idiot autoattacking everything they see without getting the last hits... sometimes with aoe spells.

You need to stay in the bushes and simply last hit everything you can. When there is a short break during the fight try to tell your ally what to do and why to do it.

They don't play bad because they want to play bad. They play bad because they don't know better.
Try to go home early (once you got your Move Quick or about 800g) to buy the philo-stone and a vision ward (the green one for 75g) maybe even boots as well. Place the ward in the river next to your lane and prevent ganks in your overextended lane. Also tell your lane partner to buy a ward once he has to go home.
Remember to be encouraging because criticism is just going to be ignored at times "Mundo feeds who he pleases!".

Shrooming gank and escape paths is more important than shrooming the bushes. Only 1 per side bush but 2-4 in the river bush and the surrounding area (risk to be ganked high due to overextension).

The shared lane (Experience):

The gold you lose can set you back massively. You really need to focus on farming and ignore the enemy sometimes. If you miss a minion kill to shoot at the enemy a little you have to watch that you did enough damage for it to be worth it. Coordinate with your lane partner so that no experience and no gold is wasted by recalling at the same time (sometimes your jungler can come and take over for a bit).
Get your Malady before you get your Mejai's Soulstealer or at least a Dagger.
Due to your superior speed ganking mid is also an option to get gold and experience (or simply relieving mid so he/she can go shop and heal).
If you manage to place some shrooms in other lanes chances are good that you get free assists/kills across the map cause if Teemo is bottom who expects a shroom at top.

You might need to sell your Philosopher's Stone earlier to get your Rod of Ages early enough.
You can start your Deathfire Grasp with Kage's Lucky Pick early to get some extra gold. (maybe even replace the soulstealer with the pick if you know the enemy is quite tanky and you won't be able get many stacks early. get the soulstealer after the Catalyst the Protector and before the Rod of Ages in this situation).

Still... don't use mushrooms to farm till they are at lvl 2.

Your lane is shroomed but teamfights happen in mid?:

Tell your solo carry to take over your lane as a solo. You and someone else from your team go mid and you start fortifying it. You can hold mid while your carry gets some more farm and exp while being relatively safe and he might be able to push your lane and kill the turret.

Even if you have 10 shrooms at bot which are never going to explode doesn't mean they are wasted shrooms. They provided vision and an invisible zone of control so you could do your part in your lane.
Map awareness is not only knowing where everybody is but also knowing that nobody is at a certain location.

You died... what now?:

So you are 2 levels behind and you are still squishy and cant do much. You are under a constant threat of being towerdived.

What you need to do is focus on shrooming every passage an enemy can attack you. Even shroom behind your turret in the small bushes, nearby creep camps, enemy escape routes.

You are now allowed to use shrooms on minions if you have a decent amount of shrooms near the turret (5-6). Not to kill them for gold but to kill them so the enemy cannot get too close. Call for someone stronger (like mid, jungler, one guy from the other side lane). carefully claim your lane with mushrooms.
Watch for your mana bar (shrooms cost mana, too). There is nothing more frustrating than someone from your team ganking the enemy you run foward with move quick and you stand there without enough mana for blind dart.

In towerdive situations use blind dart one one guy and exhaust on the other. It should give you a few seconds of tower dmg.
Farming and Jungleing

It is easier to last hit with toxic shot so don't forget to level it up. Do not attack minions rapidly after lvl 1 (exactly 1 wave + 1 minion) so you don't overextend thus preventing ganks from the enemy.

Do not use mushrooms early to farm, ever. They are too valuable and cannot kill caster minions at level 1 leaving them with about 60 HP. Later (after lvl 11) they can be used to farm creep waves effectively (still wasted if you don't farm enough minions with one and do not let your shrooms be killed by minions before they can explode).

You can solo dragon after you got your malady and a ruby crystal. The magic pen is maxed after 2 shots from malady (25-12=13 MR and you have 14.5 magic pen from runes). Remember that Dragon cannot be blinded.

You can get the blue buff but it's not necessary (unless you want to create a shroom protection field for your team before you go baron mid game without CDR). There are other allies that need it more than you do.
Lizard is always welcome but not that important. You mainly get buffs by careless junglers that eat 2 mushrooms, retreat into another mushroom while you nuke them to death. The slow from redbuff is nice though.

Teemo can jungle but he is a very bad jungler.
Working in the team

You are not the first to enter the fight and you cannot act as a good bait. "Ah hell Teemo is gonna lure us into a mushroom anyway".
If you have a good initiator you can pick off the enemy carries easily. Move Quicks active also allows you to run into a fight and drop one quick mushroom under one of your allies. Most people do not have the overview to see whats going on and the mushroom will explode turning more than one teamfight to your favor.

You can also create an escape route with one or two mushrooms and save your buddies from big bad autoattacks.
Summary

If you play him well enough you can kill almost any enemy you face on the battlefield. You have good damage output without mushrooms and are a nightmare for enemy dps squishy carries. You have free wards that deal AOE damage and a blind that shows you why Teemo is one of the best anti-carries in the game.
Take your time to practice.

Have a nice game

AnjouShin

Once again I'd like to say, this is not my guide, but AnjouShin's guide and can be found at LeagueCraft.Com