This is a very very basic guide to play teemo ap in dominion. If you want a ranged champ that is AP and is good vs Melee, specially those that depend on autoattack burst, Teemo is the champ.

I think he is pretty strong and there is a chance that he is secretly tier S. But for now I will say that he is pretty strong. His ability to control the map is unparalleled. He can use his great mobility to gank, put pressure, backdoor and defend what's neccesary, increasing map pressure, while slowing down enemy mobility with decent shroom placement.

He is specially strong vs autoattack champs, and more so if they are melee. He is weak vs burst champs.

I think 21/9/0 on Magic is the only way to go. Increment damage, while getting a defense boost. Also you need revive mastery.

Runes:
Marks: Magic Pen
Seals: HP/Level or AR/Level
Glyphs: AP/Level or MR/Level. You can put 2 CDR glyphs to reach 40% CDR with full build but that may require a specific rune page. Magic pen is a decent option if you will go magic pen quints and full magic pen build.
Seals: I prefer MS as it allows me to do what teemo do. But Magic Pen is ok to go for full magic pen build.

is a must.

After that you can go whatever really. allow you to do some 1v1 that you will do in your jungle quests. Allow you to be more usefull in teamfights in my opinion. is good if your team do not have one at least. It allows you to do some interesting move at defending and attacking points. and give you more tools to escape which you may need if you backdoor too much.

Your Objective is to reach Max CDR with . After that Damage is your priority. is of course the main way to achieve that. However it's very expensive and sometimes is more important to get magic pen and defensive items.

For Magic pen build you should go: . If you are going for magic pen build you can maybe skip Sweeper, so you can reach a high number of magic pen fast wich will give a you a lot of damage vs many targets.

Otherwise is fine. Rarely you will get more than 1 defensive item. So have that in mind when going for one.

Sometimes you can sacrifice or even in your build to get defensive items, that is though most of the times a mistake, so be carefull with that.

Teemo is a champ that should live in the jungle. Of course you should help in points whenever necessary. But his strength is definitely not in teamfights and not to be in the open.

Your work should be to put pressure by backdooring and ganking. Ganking should not necessarily mean that you will kill the target, but do damage, and push the opponent team to send people where you ganked, then you can use your extra speed and mushrooms to gain space advantage to be somewhere else.

As the game progress you will be able to put shrooms faster and faster. Eventually you can put shrooms in a way that is almost impossible to gank without being noticed and slowed down.

Sometimes like it or not, teemo will have to teamfight. He does best if he has teams with kiting potential, that will mean the opponent will jump on your team , if that is so you can shroom where they are gonna come and blind their committed AD melee. But that is just dream scenario many scenarios your team will jump in and in those teemo can only kite in and do some damage. You can try to flank the enemy team and blind they ranged ad, but a mistake here can be extremely costly.