single Lipo should be fine to get you going. make sure you get a balance charger for best results.
For your budget, you are best keeping an eye on on the "For Sale" section on here - that way you should be able to pickup some quality gear that won't need replacing as quickly. Aim for getting sensored BL motor/ESC - stuff from Speed Passion, LRP/Nosram, Novak, Tekin etc crops up from time to time and are all worth a look.
HTH
