Instead of GoPro you can use a Xiaomi camera. Check in ebay or elsewhere. Same size as Gopro, costs $80. Good reviews. For gimbal, take a look at walkera 3D at $130.
Edit: The Walkera is not as easy to install on a P2 as the Zenmuse is. So if soldering is a problem, then no other option than Zenmuse.
HTH, have fun.