buy 2x4 gb ram instead of 1 8gb stick so that you can use dual channel on the mobo. Also change the mobo to something else from gigabyte, asrock or asus. the hdd is for storage but if you have the money i would suggest upgrading to a WD black.
the biggest change is the gpu, 2gb of GDDR5 is just too little, i would get a r9 280x instead, because of mining these cards will drop in price by 40%!