It's AM3, which is a dead socket, but there are still many upgrades. I would upgrade to either an old Phenom 2 hex-core or an FX 6300 if your motherboard supports it.
As for the GPU, anything between a GT 1030 and maybe a GTX 1060 3gb would suffice.
Just get an entirely new PSU, that thing won't be doing much. Go with at least a 80+ Bronze 400w PSU.
This is all under the assumption that it isn't an SFF machine, if it is, well, God help you.