This is my Ap teemo build in which your blinding dart is the majority of your dps unless some poor soul steps on your shroom then it looks like hiroshima

I tend to go with AP pen/AP runes you can switch your seals for mp5 if your having mana problems

First off Dorans ring = decent ap and mp5 for low lvls compared to Amp. tome and a pot i sacrafice 5 ap but gain 100hp and mp5

2nd item Spell pen. boots - do i really need to explain?

3rd item Needlessly Large rod- yes it's 1600 but by this time you save this you should have 1-2kills or assists it sets you up for mid game ownage

4th item -Rabadons well im not gonna explain why

5th - RoA gives you some hp for survivability nnow that you have more hp doesn't mean u can go toe to toe with a full hp olaf be smart

6th item - Zhonya's 100 ap and some armor plus the active really makes people rage in teamfights trust me you want this due to your shrooms are tearing people up and you are the focus by now

7th item -hextech this one is optional i like it for the ad/ap and lifesteal its not much LS but a wave of minions step on a shroom you do benefit replace it depending on your team make up

8th- Lichbane mmm mmm 600-800 blind dart followed by another 600 attack? god mode 'nuff said

now Ignite is what every teemo should get the following 2nd choice are all viable depending on your make up

teleport - goto a shroom and cut someone off....con no good escape for you

flash- great escape of chase spell (my choice) con...once you flash someone always flashes with you

exhaust- great for melee heavy teams gives you mroe surv. against a 1v1 and allowing you to run away if need be .....con the cd

Always always always act like a ninja your not rammus dont initiate fights with this much ap u can easily kill someone 1/4-1/3 hp with a blind dart set up your shrooms in known gank spots and escape routes you may pick off a straggler that way or prevent or counter a gank

Red dots are river control

Blue is Jungle Control and know escape routes