All the colors just gave me a headache. j/k. Aaaaaaaaanywho, a 27t motor is fine for drifting. I started with a 35t. 12t is gonna shoot you into oblvion somewhere if you don't take baby steps first. That's a 15 turn difference. That's like going from a Civic EX to a stock Viper in like a day.

Anywhere from 19t-35t will get you sideways. It all depends what you're comfortable with. Another option is brushless. Novak SS5800 is nice from what I've heard. But, you can save money by keeping what you got.