One of the great things about PCs is that you can put pretty much as much or as little as you want into it, especially if you build your own. Personally, I would just go for a fairly old graphics card, 4-8 GB of RAM, and a decent AMD CPU. You really don't have to put too much into it to get something that will play at least a large amount of not quite state of the art games at 1080p at moderate settings (actually not bad at all compared to consoles), or fairly low settings on newer games, but at some point there may be a limit to what you can play. It just depends on how complex the graphics are, and if you find that you'd like to upgrade for better performance or higher quality, you can upgrade as you need to.