If you don't know what to get, I'd recommend the FrSky Taranis QX7, if you can spend $110. If not, then...well idk. The Taranis QX7 You will not need to upgrade for a very long time, if ever. The RX depends on the aircraft. If you are using a quad then I'd get the FrSky XSR-M or the R-XSR to bind with the Taranis. If you are building a plane with servos I would recommend the FrSky D4R-II or the X8R or the X6R. All of the FrSky RXs bind to any FrSky TX(Radio). I don't have any RXs or TXs to spare, but I am always happy to give advice.