Looking to upgrade optiplex 3020 MT for gaming.

I’m very new to pc building world and was hoping yall could help. It’s got: Core i3 4160 / 3.6 GHz - RAM 4 GB - HDD 500 GB - DVD-Writer - HD Graphics 4400 - GigE - Win 11.
I plan to upgrade ram, psu, and gpu. I’ve already got ram on the way just need help deciding psu and gpu. Please let me know if there’s more information needed.