AP Teemo requires more focus and some what skill. His Darts and poison passive allowing him to deal tons of magic damage usually without taking much back if played right. I don't like building Right-Click Win builds because they are really boring and easy. AP Teemo is what its all about and its how he should be played.

Pros:
Massive damage
Able to pick Enemies off
Fast and Stealthy

Cons:
Squishy
Can get demolished by Burst AP (again squishy)
Focused Down Usually

MP=Magic Pen
MR=Magic Resist

9 Greater Marks of Insight: 8.55 MP

9 Greater Seals of alacrity: 6.84% Increased Attack Speed

9 Greater Glyphs of Shielding: 24.3 MR at 18

3 Quintessences of Insight: 5.67 MP

Passive: Camouflage Nice for ganking and can save you if your on the run. All you have to do is get into a bush and go stealth in time before they catch you

Q: Blinding Dart Blinds and deals magic damage to your target

W: Move Quick Speed You up for a short duration. Gets you from point A to Point B.

E: Toxic Shot Gives your auto attacks DoT.

R: Noxious Trap Your bread and butter to Teemo that deals a good amount of magic damage and slows who ever runs into this baby. Don't rely on this too much!! Good for the map control as well, just like wards.

Sorc Shoes <$1100> Great boots because of the MP.

Kage's Lucky PickKage's Lucky Pick <$765> Gives good AP and a decent amount of money over time. make sure to keep this until your last item then you can sell it for your last item unless you decide to get rid of it earlier but i suggest you keep it.

Malady <$1825> Gives good attack speed and reduces enemies Magic Resist.

Rylai's <$3105> I only get this item because of the Health and AP it Gives, Not really for the slow but who cares you get the things you want with the extra bonus.

R. Deathcap <$3600> Gives a ton of AP and increases the amount of AP you have by a Percentage.

Nashor's Tooth <$2885> Gives a good amount of attack speed and CDR. You can trade this for a different item if need like a M. Evil Tome.

Hextech Gunblade <$> This item is expensive and i don't get it for the slow but i do get it for the little AD and AP it gives, I suggest this item because you spell vamp and life steal off it. Great for Teemo.

Zhonya's Hourglass <$3100> Gives a good amount of AP and its active can save your Squishy ***.

Void Staff <$2295> Get this item if they are stacking MR. Void Staff will cutt their MR almost in half. Guinsoo's works great with this item if they stack MR!

Abyssal Scepter <$2650> I suggest this item if your going against heavy AP nukes such as Leblanc and Annie. Their Burst is Rape QQ :(

M. Evil Tome <$2350> Good item that gives both CDR and AP. I suggest this item if you don't want Nashor's.

Lich Bane <$3470> Sort of expensive but it gives good stats such as some MR, AP, and the passive of the Sheen but its upgraded. I suggest this item because of the passive!

Guinsoo's Rageblade <$2235> Great item but i don't usually get this unless they start stacking MR.

Haunting Guise <$1485> Gives some health and another 20 Magic Pen

The First build is what I usually build but you might have to switch outs some items.

The second is good if they are stacking MR. Your shrooms suffer more and don't get as much damage from the Rage blade but its great for going against Heavy stacking MR champs. This build has a lot less Attack speed so you can switch out the Lich Bane if you need more Attack speed.

Flash: Main spell i get even though it has a long CD can save your life and get you a kill so I suggest taking it.

Teleport: Great spell for Teemo because he can Teleport to one of his shrooms and pick off kills or gank a enemy

Ghost: Don't suggest this for teemo since he is already fast and his "W" is sorta like ghost. Has a lower CD than Flash so take it if you want.

Heal: Not useless since Teemo is Squishy.

Ignite: I never take this for Teemo but i see a lot of teemo taking this but theres no need since teemo already has a DoT Ability from his auto attack.

Cleanse: Good Spell to save your *** from getting stunned and beat the hell out of.

CV: An okay spell but usually your supports take this so grab a different spell. Take it if you want.

Exhaust: Great spell if your going against fast/ Auto attacking champs like Kog'maw because it reduces attack speed and movement speed.

As an AP Teemo Make sure to Shroom as much as you can. If your mid then its impossible to gank you at 6 because u have free wards that deal damage. If your on a side lane then make sure to Shroom up bushes, the River, some of your jungle and some of their jungle. I suggest that you even shroom up the mid lane to help them out so they don't get ganked.

If you like to annoy enemy champions then Make sure to auto attack them then hit them with a dart. Go for the Squishy champs first! If your fighting a champion like Ashe or any champion that uses Heavy Auto attacks then make sure to blind them to reduce the amount of damage you could take.

NOTE!!!

You Counter Master Yi Hard with your "Q" So make sure to Dart him when ever he is attacking your team.

Other than what I written all you do is the normal things like Fighting and Last hitting minions to get farmed up.

AP Teemo can do tons of Damage and the Best way to build him is exactly like this. I have seen and read other builds and most of the time they focus on Shrooms. Not only that every other AP Teemo i see in game relies too much on their shrooms and not enough on other things like your dart. Always rely on your "Q" and some what of your DoT.

Last Thing:

Don't worry if someone gets an oracle because that doesn't mean your useless. I build and Play AP Teemo so that if someone does get oracle then he cant just dart someone to death. Usually people get oracles to eliminate Teemo but not once has it ever got rid of me! So don't Worry about that noob Oracle!!

Hope You learned something from this guide!
Have Fun and Good Luck with AP Teemo