7870 ~$200
Amd phenom ii x4 965 $95
Asrock 970 extreme 3 mobo $80
8gb ram ~$60
Corsair builder series 600w psu ~$70
That build only leaves you. ~$95 bucks for a case, hdd, and disc drive though, assuming my guesses on the prices are right. Idunno why i even post from my phone, i get too lazy to research parts haha. But the only case i can think of thag is under 50 thats worth buying is the nzxt source 210.
Maybe downgrade to a 7850? My buddy has one. Plays farcry 3 max settings, dead island max settings, and crysis 3 and medium-high settings all at 1080p.