Will you build it yourself? Seems like you didn't require that much parts at all, like HDD, OS, stuff
As Hunter315 Said, the only thing you probably will need is the Mobo and a "crappy" cpu? And maybe even a Graphiccard, depending on your "Light Gaming"
I know complete, ready-to-use computers from like $4-500, including everything+OS
The entire thing depends on your need of items and skills of buildin if you ask me