I HIGHLY recommend the Sakura XI. I'm currently racing with one, and also own the older Sakura Zero S. Both are SUPER cheap and very competitive. Also, they're freaking tanks. I've only broken twice in over 2 years of racing/practicing with them at the track and I've had some straight up gnarly crashes.
With a few aluminum upgrades, they're super competitive and extremely cheap.
Also, I LOVE my Turnigy lipos from Hobbyking. They work as well as any other packs I've tried and I have the same speed, power and runtime as the other racers who use more expensive packs. AND, they're typically lighter to boot!