Ok, so this is a fun guide not a serious one. The focus between the two builds ( item and skill ) are too show my favorite AP Teemo styles. The first primarily focusing on utility in Team fights and the second as a nuisance.

Legend:

MR = Magic Resist
SP = Spell Pen
CDR = Cool down Reduction

AP = I hope you know what this is (Ability Power)
AD = ^ ( Attack damage )
AS = Attack Speed
SS = Skill Sequence

The rune selection here is focusing on early game damage. with the 10% from masteries and the 18 from the runes you basically increase your damage to 100% because at this point the enemy has not MR unless they have taken and item for it off the start / or they have MR runes. In either case the SP is great for early game.

You are not likely going to be a carry in this game so might as well be the next best thing that Teemo can do. Support. With the 9 points into OFF you get a nice little bump of AP ( makes a total of 11 with the runes ) 10% SP and 6% CDR. More than likely you will not be getting alot of kills until late game so the experience / extra gold from assist is the most beneficial path at this point point.

the first set of items ( sheen - void staff - lich bane ) are focusing on the hang back in a team fight and disrupt their AD Carries / Tanks style of play.

the second set ( 3 arch angles ) is my personal favorite in PvP. This focuses on ALOT OF AP and MUSHROOOOOOMS !


Both in clude MAX CDR so you throw down the shrooms every 16 seconds and blind dart your way into and out of trouble.

I did not include AS items as they are not really viable when you are looking to this amount of AP and as a support. Maybe another guide focusing more on a AP AS Master Yi Format will be created and Teemo honorably mentioned as a contender for that item build.

For now 1.0 AS will suffice.

First SS goes with first Item build ( Blind Dart Focus )

Second SS goes with second Item build ( MORE MUSHROOMS ! )

As AP teemo you get focused alot, especially if you get good being AP and become very disruptive in team fights. so flash + ghost = survivability

Pros:
Very solid early game
If done right, Amazing Late Game
Mushrooms piles of 10 or more can almost anything with less than 3k health
BLind dart is a game changer

Cons:
Very team dependant
VERY Squishy
Requires patience and planning

Best to lane with with a carry or tank against Melee champions rather than range unless the range is an Auto Attack and win champ like ashe vayne or Kogmaw.

Try and sit in the back and poke when ever you can, avoid all damage if possible, play very defensively , your turret is a best friend until level 6 when you can start zoning more effectively with mushrooms. Make sure your lane mate knows this and be smart, watch for the baits.

I highly recommend laning with someone and NOT SOLOING.

in team fights look for the Carries ( if they are being aggressive ) and blind dart them, try and disrupt them as much as possible, be careful to get ahead of your team, especially the tank.

If the carries are hanging back , just poke the tank and use this time to throw some mushrooms down to help cover a retreat if needed.

Well I hope this guide helps in your LoL experience. Meant to have fun with not too serious, Like any champ, experiment, get to know this build / style of play and see what you can and cannot do. any questions feel free to ask in the comments and I will try to answer them as best I can. Thanks for reading.