I think his graphics card OK for no until he's able to get a extra 150 or more for a good gpu because the 9400 get preforms like 210 and that's OK medium to max on cod so now I recommend a i5-3570 non k and cheap motherboard and one stick of 4gb DDR ram instead of duel so cpu=220 + motherboard=70+ ram=20
You currently have a core 2 quad? If what you want to do is game then I would leave the current system, but upgrade the graphics card, something like at least an ATI radeon 7850 and a nice power supply. That should give you a nice gaming upgrade, then save up and get a nice board and CPU. You can go with an i3 or amd APU, but not sure how much better those would run than your quad.
I would say video card, power supply, possibly an aftermarket cooler for overclocking and a little extra ram if you have a little cash left after those. That would pick up your gaming performance I think by quite a bit, and give you a bridge to a new board and CPU you really will be happy with later.