ok so here's what i built for 500$:
https://pcpartpicker.com/list/qqTbPn
Also the cpu is not 50$,its around 170$.
For the GPU i would stay gtx 970 4gb,because it can still hold well in modern games.So instead of putting a new gpu in the build i made sure that the cpu,mobo,ram were on point.I choose ryzen 5 3600,because its bassically the ultimate budget cpu,i went for b550 just because its better for future proofing that b450,also went with 16gb 3600mhz ram because why not,it can only do you good.Also i put 480gb m.2 in there for windows and some games+that hdd of his can be also used for games.I didnt put a new PSU in the build,because i though if it can already handle the gtx 970,it can handle this new stuff to.But keep in mind that when replacing the gtx 970 for something new/better he will need to replace the PSU since the new/better GPU will require more power.Also another reason i didnt put the GPU in the build is because new GPUs are coming and gtx 970 can game on everything (atleast i think).What do you think about it?