Upgrading parts help

Hello, ive had my pc for a while now and the only games ive really been playing on this is either css or CS GO, the problem is i get very low fps on cs go so its quite hard to play, whats the best way to upgrade it?

about 2 years ago ive bought a new gpu and new graphics card for it, hoping itll give me more fps but that failed.. whats the problem, what other parts do i have to change?

The model is Dell Inspiron 570

Operating System
Windows 7 Home Premium 64-bit
CPU
AMD Athlon II X4 630
Propus 45nm Technology
RAM
6.00GB Dual-Channel DDR3 @ 533MHz
Motherboard
Dell Inc. 04GJJT (CPU 1)
Graphics
DELL IN2010N (1600x900@60Hz)
2048MB NVIDIA GeForce GT 610 (ASUStek Computer Inc)

ive changed the graphics card to GeForce GT 610 and a PCU to a 600w 2 years ago

I currently get about 70fps on CS GO on lowest settings, is there anyway i can just upgrade some parts and get it maybe over 100? Thank you

Upgrading parts help