a good computer for gaming will either sport FX 6300 Overclocked or FX 8320/50, OR on the intel side an i5 4670 is a great choice.
For a graphics card (gaming matters most here) you want something like a GTX 660 or better (I.e 670, 680, 760,770,780,780ti) this will depend most on budget but since you don't mention one the 780ti is the strongest gpu out there right now. On the AMD/ATI side of graphics cards you want an HD 7870 or better, or a r9 270x or better (basically the same thing) (so i.e r9 270x, r9 280x, or r9 290x).
8GB RAM is the sweet spot when it comes to gaming, so 2 x 4GB sticks of 1600Mhz RAM or 1866Mhz is even better, get ram that defaults at 1.5V or lower (higher quality RAM).
for the power supply you want 550W minimum for headroom, and 850W if you ever want to run two graphics cards side by side. the bigger and beefier the graphics card, the more power you will likely need. Some quality brands for power supplies are SeaSonic, XFX, Corsair, Antec, CiT, Super Flower, Silverstones.