Doesn't matter at this point since your build has to be max $500. AMD is the solution since it's much cheaper than Intel, though I would go with Intel if you had the money.
Done, you don't need anything else. That's about $370. Plus tax, roughly $400. You may need a new hard drive if you require that. The PSU (Power Supply Unit) should be at least 500-600W for a good and clean power.
If you are doing wireless, you will require a wireless card, if not use the LAN they have on there. Good Luck.
And buy these specs, what standard would most games run? (low-med-high)