The following is what I would call minimum for general 3D emulation and light gaming. You could get a graphics card used for cheaper but I was just going with what I could see on amazon. These Dell Optiplex PC's can be found on Craigslist/Offer Up/Facebook for cheaper as well.
Graphics
Radeon RX6400 - $150
or
Nvidia 1630 - $150

PC:
Optiplex 7020 - $100