Graphics card help

Hello, I am building a pc. I am going by the 350$ Gaming Rig video on the RazetheWorld Youtube channel. Instead of just using the built in graphics on the AMD apu, I was going to buy the Asus HD Radeon 7750. I was thinking since this is going to be used for playing games if I would need the AMD apu, or if I could get a faster CPU for cheaper.

I have a 7770 and it runs most games 1080p on high at 40fps, 7750 I think does it at arounf 25-30 so yeah.