need pro tech advice.. pls...

[Holybread]

I'm not good with specs and I bought this buget pc on frys which I know I payed a little more if I built it myself... but I don't know how to do it...    I wanted to play the game on max where I can stil move around with less lag...   I can't even do grandharvest raid cause I froze even on control F mode...   what should I upgrade/change to make my system a little better... or can I do something on my system on this spec to make my fps a little better... when I'm on mushin doing towers I get 90 fps but when I hit the spot where it is crowded it dropped to 20-30fps... and on dungeon it drops to low 40... pls help...     so here are my specs...     Processor AMD FX-8320 (3.5GHz, 4.0GHz Turbo) Processor Socket AM3+ Processor Main Features Turbo Technology, Hypertransport Technology Cache Memory 8MB L3 Motherboard 760G Expansion Bays Total (Free) 3 x External 5.25", 3 x Internal 3.5", 3 x Internal 2.5" Expansion Slots Total (Free) 1 x PCI-E x16, 1 x PCI-E x1, 1 x PCI Interfaces   RAM 8GB DDR3-1600 Storage Controller N/A Hard Drive 1TB SATA-3 7200RPM Optical Storage 24X DVDRW Graphics AMD R7-370 Video Memory 2GB Digital Video Standard 1x HDMI, 2x DVI, 1 x Display Port Power Supply 500 Watts Audio Output Flexible 7.1-Channel Audio w/ jack sensing Networking Supports 10,100,1000Mb/s (Realtek PCI-E GbLAN controller RTL8111E)