Electronize do quite cheap ESCs. If you're using two drill motors (one on either side), I'd recommend two 15a, if you're using 2 drills in each side, 2 of the 30a version. Some people prefer more precise ESCs, but for most they're plenty good enough.

They're also pretty robust, and aren't too huge.

I'm using two 30a Electronize ESCs with 4 drill motors, and the Planet T5 Transmitter and Receiver set. So far I couldn't have asked for more, I don't have much or any experience with other setups but as far as I can tell, what I have works great. And it's all relatively cheap.

I'd recommend having a good look around the FW forums, and build diaries. You'll realise that you're in exactly the same position as loads of others, all asking and wondering the same things as you. Or, you could ask around for when the next event that is near you is happening, tag along and ask questions, I'm sure there'll be people willing to give you some advice.

Hope I helped...