http://www.pcgamer.com/build-guide-the-best-cheap-gaming-pc/

PC gaming can be expensive, we know, especially when you're brand new and don't have a previous rig to upgrade or retrofit. This build is aimed at creating a gaming PC that performs decently well for as little money as possible. It cuts corners on any sort of bells and whistles, opting purely for components that provide the best performance in the bottom price tier. Long story short: this is the best gaming PC build for $500.