that depends on you. If you get a new radio you can buy one on the same frequency and use the servos and rx you have now in another plane while using the new radio. If your radio now doesnt have dual rates, expo, or mixes you will be fairly limited in your future planes. (at least getting the most out of them)

However, the radio gear goes in late in the build so just start working on the kit and learning on the trainer and then you will have a good idea of what radio, servos, and other setup stuff you want later on.