This is an AP teemo build that focuses on map awareness. I will usually start off with boots of speed and pots and try to get malady/kages asap. By the time you get boots of lucidty you should be able to farm the mana buff which will help you poop shrooms until you get your chalice. After that you get rylai's for survivability (make sure you get the health belt part first) and then zonhya's and dfg. After youve accumulated enough money for the death cap, SELL chalice and get it. This will usually keep you alive if you play smart, as the longer you stay alive, the more shrooms you can put up on the map.

Exhaust and Flash work best

Flash is necessary. Always. Teemo is very squishy and needs flash for survivability.

If you find you are still dying, opt for heal; this works really well if someone tries to turret dive, as you should have shrooms in place for turret divers. They dive, you heal and they get shroomed and die.

Other good spells:

Teleport: since you can teleport to shrooms, u can use this to backdoor and catch runners on the way back to base

Ignite is ok too, but I find the other spells to be more useful.

Pros
-smart survivability
-good early game damage with malady
-amazing map awareness (opposing team getting baron is a rarity with this build)
-very effective against noob players (they chase all day long)

Cons
-Mid game can be weaker due to getting mana regen item but it pays off a lot in late game, and you shouldn't be dying too much with all the shrooms around anyway
-still squishy-ish

Teemo's passive makes him invisible. This is very useful. If you are low health and being chased, sometimes its just better to stand still than plue pill.