Best for that mobo if you dont wanna upgrade to xeon or c2q ( like Q8400, Xsomething, see like on 771to 775 delided) R7 250 1GB GDDR5 ( not ddr3 care for that),
If you are gonna upgrade max 1030 (GDDR5), GTX 950/960, R7 265, GTX 750Ti, 750.
That is my suggestion, also which PSU you have?