Hi and welcome to my AP Teemo Guide, this is my main build for Teemo and is not hard to use.
Teemo is a ranged, support character and with the help of your shrooms, the kills and assists would be easy for you

As far as yordles are concerned, there is something slightly wrong with Teemo. While he enjoys - and in fact needs - the level of community and companionship inherent to all yordles, Teemo feels it so strongly that he ventures out on his own to destroy the enemies of Bandle City. There is something that switches off in Teemo, so that the lives he ends do not burden him. It seemed only logical to send him to fight in the League of Legends as the champion of Bandle City. He has taken to the League like a duck to water, seeking out the foes of the yordles and extinguishing them with the rare ajunta poison he personally gathers from the jungles of ***ungu. However, the limited company of his own kind wears on Teemo, and cracks are beginning to show in his innocent and chipper fade.

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

Marks
Greater Mark Of Insight is used here because, teemo's autoattack, blinding dart and his shrooms are magic based.

Seals
I use Greater Seal of clarity, because sometimes your autoattack can not do the killing blow or the enemy team is harassing a lot and they are melee based, i often use blind quite a lot making my mana deplete pretty fast.

Glyphs
I use Greater Glyph of Force, because it increases the starting AP by 2 or 3 and if you intend to be staying in your lane a lot and farming, this would be great for your poisons.

Quintessences
I use Greater Quintessence of Potency, because this gives me an intial starting AP of 15 also added with the Glyphs, your starting harassment should be very good.

I go the basic 9-0-21 caster build for teemo.
An overall Summary of the Mastery Tree, is that it would give you:-

Offense

0.66% Crit Chance
0.60 AP per level
3% Cooldown Reduction
15% Magic Penetration depending on Targets Magic Resist

Utility
Increased Hp Regen and Mana Regen by 4%
Increased Duration of Ghost by 1.5 seconds and Ghost Movement speed by 6%
5% more Xp
Increased Mana Regen per 5 secs by 3
Increased Duration of Buffs by 30%
Allies will get the same amount of mana from your Clarity spell
Increased base movement by 3%
6% cooldown Reduction
Reduces Recharge time of summoner abilities by 15%



You get 9% cooldown reduction in total from offense and utility.

Dorans Blade - this item is good for early game giving you 3% lifesteal, 100 Hp and also 10 Damage
Boots of Lucidity - Often i lane long enough for these boots or i just buy basic boots and recall when i have enough
Fiendish Codex - Since we are going to do a cooldown reduction build i choose this for AP, Cooldown Reduction and also mana regen.
Stinger - I build this for attack speed and cooldown reduction.
Needlessly Large Rod - i usually get this for the amazing 80AP boost at early game
Blasting Wand - i build this so i can complete my Rabadons Deathcap
Rabadons Deathcap - +155 Ability Power UNIQUE Passive: Increases Ability Power by 30%
Frozen Mallet - I usually get his for autoattack slows and hp
A Rabadon stack would give you a lot of AP at late game.

Clarity
I would recommend clarity for mana if you dont really have much mana regen runes.
I also it to bolster my allies mana supply in teamfights or before one.

Ghost
I have tested this quite a lot, you might say but teemo has a w for the sprint.
If you were playing a nuker, for example LeBlanc, the leblanc popped her ghost getting ready to nuke me, but i also had improved ghost and a w so I would have not died ^^

Flash
I suppose this would be good but there is a massive cooldown for Flash, but only 3 minutes for ghost.

Ignite
I guess you could use this with your passive

This section is used for your shrooms, by the end of all your Cooldown Reduction, the shrooms will be able to be used at 13.2 Seconds.

If you are doing good late game, you might want to disappear for a bit and starting shrooming there jungle, this would give you a chance to steal buffs or kill them when they are running from the buff.
I often like to spam shrooms at baron, this often gives us initial damage of 1k from the shrooms. If they stay there, there hp would be pretty low and it should be easy to steal the nashor baron buff as well.
You should try and place shrooms near corners because most players use corners because its quicker. If your mid shroom each bush with 3 - 5 shrooms on each side

Thank you for reading my build, i hope you will be a good teemo from this build and own the world with you shrooms.