In the Crystal Scar map of Dominion your main objective is to control & capture towers. This build is to influence 2 types of Teemo personalities:

Defensive Teemo in tower control while dropping your enemies defenses with The Black Cleaver. Upon armor shred you tack on your poison tick counters along with Malady's ticks for a steady hit point loss. When you finally get backup you can focus on one or more enemies to slow their retreat with Frozen Mallet and assist your allies in team domination. When you are on defense duty though you can try to turn a enemies tower by yourself only if you manage to kill the other enemy hero and you can see the other enemies on the map away from you otherwise just return to your tower and keep throwing down shrooms in key places around the tower. Never put them inside the tower platform because if they do manage to claim the tower your shrooms will be seen and then destroyed.

Offensive Teemo is the one I prefer. Your speed passive/click speed boost is key in this build. Your main objective is to make your enemy recall to base to recapture towers you had turned to stem the tide in your teams favor. Ganking heroes is not your main concern. Tower control and blinding enemies is your concern. If you get in a big fight with your allies versus the enemy just blind 1 or 2 enemies then peal off combat to claim a tower that's now being neglected. This will cause 1 or more to disengage from battle to reclaim the tower you had neutralized/claimed then give your allies a better opportunity to win their confrontation. Offensive Teemo in a nut shell is to be a major thorn in their side all game and to only supply support for you allies.

Spell selection:
I usually get Ignite all the time. It's an awesome spell to turn Nocturne or any other hero life gaining out of the equation and it's level tick is pretty good to finish off heroes too.
The second spell is up to you. I will swap between exhaust if I know I will be on defense duty on the bottom tower otherwise I choose Ghost to be offensive Teemo. The Ghost spell does stack with your spell ability and the map speed boost so if you have the Phantom Dancer in your inventory you will have a pretty crazy speed boost that could revival Master Yi.

If you have any comments or criticism please express yourself I do enjoy reading the responses and I know I'm not perfect but as a human I will learn to adjust and make changes if they seem reasonable.