I have a DJI Phantom 3 Pro Remote controller, I am building a Racing Drone and I have bought everything else except for the transmiter. I there a chance of using the DJI Transmitter for the quadcopter I am building and what kind of receiver/transmitter do I have to buy to make it work?

The racing copter's receiver must be able to bind with the Phantom's R/C, which could be tricky. I would suggest getting a DEVO 7 R/C, it's very configurable and works with a range of receivers.