I don't have the greatest setup due to money constraints, but it is an ok rig. The performance I get is not great. I run 45 fps in good spots. NPC's lag out, mobs pop up much later than I arrive, skills activate but I dont see them on screen. I'm not super tech savy so what do I need to get better play? Is is Lag or performance?

Processor- AMD Athalon II x2 220 (2.80 Ghz)
4 GB Ram
Nvidia 550 Ti