If you want a good entry pack check out this one:
Or if you want more punch and capacity:
What chassis are you using? The size that your car can physically hold will determine how much battery capacity you can buy. The first battery is part of the 1st generation of lipos and is still plenty good for most applications. The second is part of the second generation of lipos and performs a bit better but if you are just starting out, no reason to spend the extra money.
Make sure you have a charger that is Lipo friendly and once the pack feels like it's losing punch, pull your car off the track and charge the pack - running it anymore can damage the pack.