You have to know that:
1.Always Blind the opponents when they are following u!
2.Don't go close to the enemies! Try to be in range!
3.When u go in team fight be sure to occupied back road with mushrooms so if your team retreat they can't catch you!
4.Use mushrooms for camera in jungle so you will know when exactly they are coming for gank!

SUMMONER SPELLS

Ghost

: I think Ghost is very useful when you retreat and when you attack, too. When you set mastery point on Haste, you improve Ghost with 8% more speed and 1.5 more duration so you have 27%+8%=35% more speed with it.

Ignite

: I use Ignite always when I can. If they are low it is very useful with one normal attack. Because of your normal attack he is poisoned for 4 seconds and because of Ignite for 5 more seconds. This is often deadly! When you set mastery point on Burning Embers, you have 10 ability power while Ignite is on cooldown. Ten ability power in early game is not unnecessary.

Mastery points

I think this is the best mastery points for AP Teemo. Cooldown reduction is very useful always!

Runes

Runes for magic penetration are one of the most important things for more DMG such as runes for Ability Power. Cooldown reduction I already said is very important always.

I think this is all. If you have questions/suggestions just post them here!

I am sorry for my bad English! I am Bulgarian!

As they say: ''Though he is known as the Swift Scout, it is clear that Teemo is actually something else - the unrepentant assassin of Bandle City.''

MUSHROOMS HERE, MUSHROOMS THERE, MUSHROOMS EVERYWHERE!!!