If money's tight, buy a basic 4 channel radio. Later, when you know you are serious about the hobby you can buy a computer radio on the same frequency and use the stuff from the first radio as a second flight pack. In some cases, you can even use the transmitter battery pack in the new radio.

If money is not a problem, buy a basic computer radio. This will get you through several planes, and possibly a lifetime. Even on a 4 channel trainer, a computer radio will offer several advantages such as electronic trims, end point adjustments, dual and exponential rates, and throttle shutoff (a handy little switch that kills the engine).

If money's no object, buy the latest 9 channel wiz-bang setup you can find. This way you can impress everyone at the field while flying your 4 channel trainer