Welcome to RCM!
Around here, hobbycity packs are accepted for the price, and hyperion are the best you can get, and won't break the bank doing it. Flightpower packs are also amzing. Stay away from maxamps or your cat will have bad luck for 7 years.
4s is enough for racing. It is lightweight and it'll get the job done. You could run more, but it's just extra weight and power. I would start off with a 4s pack and if you're not happy you can get a bigger battery I guess.
And make sure to use spaces and capital letters man. Some of us around here are grammar freaks.
