I'm using a tarot T2D gimbal, it has a gopro cable included, and i bought a 5.8G transmitter for 20€, (very weak but form my use is perfect), for a ground station there is a boscam lcd screen with integrated 5.8G receiver, for around 150€, it works perfectly, gimbal bought on ebay and rx and tx on hobbyking... i think you can buy all for around 300$ maybe a little bit more...
the only problem is that the tarot is a little bigger than ideal and i had to extend a little the landing gear of the phantom