With this build you will dominate the solo lane in 5v5 or 3v3 gametypes. Teemo will have amazing attack speed(2.2-2.5) and amazing damage/armor penetration. This is a ganking/solo build.
In a nutshell, this is what you need to do to own soloing with Teemo. Once you hit level six you've unlocked your mushrooms, they do a lot of damage and slow people. Right when you get the move start planting mushrooms everywhere, always on the inside of the paths. They serve as great scouts seeing as they're invisible and uncover some of the map plus they can slow a runner down to guarantee a team kill. When you teamates call mia and someone is about to gank you from behind this is good, it means you can run away into a mushroom turn around and kill him before he ever touches you. I call that "mushroom baiting". As long as you mushroom bait you will get many kills and will be fed early on.
This build is particularly deadly mid-end game, although it is quite good early game. If you are playing a 3v3 with him you can solo the dragon right when you get your malady.
THINGS TO REMEMBER:
Teemo is a great baiter
Mushroom baiting
Always blinding shot a meele character (such as jax) right when they start wacking you in the face.
Poison Spread(hit every minion in each wave once and let you're poison weaken and kill them)
When you get runes make sure most of them are in attack speed and some of them in Damage/Armor penetration