Need Help With Gaming PC Setup

Hello,
I just got a new pc of a friend and im trying to get it to run games like MW3,Borderlands 2 and stuff like that. This is the spec list.

8gb DDR3 Dual Channel RAM

3.3ghz(3.9ghz Turbo Mode)
6x Core AMD FX-6100

Gigabyte GA-970A AM3+

Gigabyte AMD ATI Radeon HD 7950 3GB R795WF3-3GD

Antec 250w Continuous Power

Im getting real low fps in game and also takes its time loading the game, i have no idea what do upgrade.What would the best idea to get it running games with no problem ?
Thanks for your time and anwsers.