The feeder cable that ran up to our breaker box was almost an inch and a half thick. It took two guys to lift it onto the truck. The same complement on another circuit for backlighting, and still have a circuit for 3 or 4 leko's up front to cover the singers and soloists in the group. If you are unsure if you have enough power of that it's properly distributed, be sure to turn all the lights on and crank up the sound system and let them cook a little before you try to do a show with your system. You may have to talk to an electrician if you need additional capacity.
Dimmers are cool.
Most home dimmers are a maximum of 500 watts each and may cause guitar pickups and other electronic equipment to buzz. These are cheap at the hardware store, but I'd advise you to stay away from them. They can be little expensive up front, but they add a wonderful range of subtle dimension to your lighting schemes. Most professional music shows use this type of lighting to good effect and it will add a touch of professionalism to your work if you do the same. If you are strapped for cash, start with fixtures and add dimmers as you can.