For a reasonably priced transmitter, check out one of the 6 channel Futaba's or Hitecs. Hitec HS-55's are good servos and they're not too pricey. You can usually pick them up for anywhere from $12-$16 each. You'll need at least 3 and possible 4 depending on the plane. The lipos depend on the plane and motor that you're getting. Overall, I think that your best bet would be the
www.fancyfoam.com Ultimate Bipe and their full package that includes the motor, servos, receiver, battery, etc. It might even include a charger, but I'm not sure.
Warning... no matter which way you go, it probably won't be cheap, and if you're like most 15 year olds that I know, money is going to be your biggest problem.
Another solution might be to see if you can pick up a used Typhoon on ebay or someplace. The entire package with a transmitter usually costs about $220 new, so you might be able to find one used, but it's not a biplane.
Good Luck!!
Bob