Recommended upgrades to pc for dayz

[Irishpaddy]

I have a dell Inspiron 660 with a : 1tb sata hard drive, intel core i5 3330, 6gb of ram and a nvidia GeForce gt620 with 1000mb. I play dayz a lot along with other games and I'm getting bad fps rate in these games ( highest I've seen it was about 15fps) so I'm looking for some way to upgrade my pc to get better fps. What's your recommendations.? ( would like to keep cost down as well)

 

[popatim]

put in a gaming class gpu - the 620 is home theatre. drop in a 750Ti.