You can go on eBay and find really good deals on 970s or 980tis. I definitely recommend staying away from APUs, I find them lack luster performance wise. I'd recommend a Ryzen 5 1600 paired with either, as an example, a 970 or 980ti. I just built a kickass Xeon build with 6 cores at 3.8 ghz with a 980ti for about 700 and it destroys in games and even heavy workloads. Usaed hardware as of right now, for GPUs and even ram if you are lucky enough to find some, is the way to go unfortunately. Now I don't want to preach that you should go with an old server Xeon, but they are really good processors, if you know how and what to pick out, since there are a lot of them. You could do a simple google search, but a Xeon, circa 2013-present, with less cores/threads, and a higher clock speed, will be amazing for gaming, that be it, paired with a good motherboard and GPU. A perk for building a Xeon build is the ECC memory is really cheap, just make sure if you were to go that route to make sure it is clocked at atleast 1600mhz.
If you want help parting out a build PM me and ill be happy to help you.