Now, I really think I don't have a good enough psu, but I don't have too much money to spend. so Im looking for one around $50 that is compatible with my system(775 socket) does anyone know any good ones?
you should look for a psu from a good brand(antec, corsair, seasonic, ocz) with an 80+ certificate, also one that has a 6 pin connector for your 6850. Make sure the psu can deliver at least 30A down the 12V rail(s).
as for the motherboard, any psu should work with the motherboard 775 socket motherboards are pretty standard.