I would say hold off until you get your new controller.
Even if you got a UNO you would still need the driver shield (Have multiple variations here) and to be honest I prefer my machine with the supplied GRBL board.
Think you would be better off spending that money on some push buttons and limit switches.
Being so new to this I am almost certain you will need both of them at some point in the near future and they may well save you some problems with crashes !