RE: New to 2.4 buying on R/C
I use Spektrum myself, but going to 2.4 with them Futaba, Airtronics or Hitec is a good way to go. No Freq. pin issues or shootdowns possible.
Unless you want to move and reprogram Rx's you will need to buy one per plane however. This can add up but you get benefits like having your trim settings saved digitally so you don't need to retrim after a slider moves.
As far as buying used stuff, I'd rather buy this kind of item from someone at my field rather than a seller on RCU or Craigslist, but that's just a personal preference of mine.