You always get what you pay for, and if it seems to good to be true it probally is.
Buy a battery that you can afford, with the highest MAH rating possible.
The higher the mah rating the longer the runtime and usually you will get more power as well. As for the battery charger, talk with the sales person or read on line, and make sure that it is the proper charger for the type of battery your buying.
Its not rocket science, But if your looking for advice on what everyone feels is best, you will get a million differnet opinions.
My non biased advice is buy the largest mah battery you can comfortably afford and buy a charger that will work for what you bought.
Original RC 10T, T4, RC8Te, Tekin RX8. Losi Ten SCTE, Slash 4x4.