Ok I have to run. As far as a cheap case goes look for a Antec 300 Illusion, Coolermaster Haf 912 or Elite 430, Rosewill Challenger or Thermaltake V3. There are plenty more.
For a power supply check Corsair, Antec, Seasonic, PC Power and Cooling , XFX, Enermax, or Silverstone. You need 450-500 watts.
Check here for graphics cards.Stay in the $100 to $150 dollar range. The more expensive the better it will run your games. Anything over $150 is probably more than your CPU can handle.http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107.html