Ashford, according to your profile you have a Macbook Pro. You don't even have a case or a PSU or Windows OS or anything to save a few bucks on a $500 rig, much less what I would call a gaming rig. You're going to have to get about $700-$800 to get into a new system. A $100 monitor will get you 1366 x 768 resolution or 1440 x 900 res. Intel 2120 CPU and decent motherboard for $228. You need a case and a power supply, about $100 to $140. Then you need a hard drive, $85 and Ram for $30 and finally an OS. Windows Home Premium OEM is $100. That's $635 right there.
OH! You need a video card. A Radeon 6770 is in the $100 range.
You might need to alter your expectations.