You are stuck on a platform that has only 2 cpu's that can properly play modern games without issues. But they cost a ton on the used market. Often a switch to am4 is just as much if not cheaper for more performance.
A gpu ugprade would give you more fps but you will IMMEDIATLY run into your cpu limiting you.
However a 500w psu limits the upgrade potential too and I assume its an evga w1 500w? If so that needs to go.