out of those two options I would say the same thing as justin. if you have a fresync monitor then go AMD, otherwise just go with the 770. However, you may want to go with the AMD for the 4GB of VRAM vs the 2GB on the GTX. But, when it comes to overclocking either to get the most out of them, the 770 is going to require a lot less watts than the AMD so that's something to think about. If you don't have freesync and are going to play games in 1080p at medium settings and don't feel you need more than 2GB of VRAM then perhaps opt for getting a GTX 1050 like norcalsc said and overclock it. If you can find a way to stretch your budget or can find used locally a 1050ti within your budget then go for that.
But that's about all the info I have for you.