bang for the buck upgrade

[Zach Elipse]

Guys, it has been 3 years since i upgraded my main pc and now i want to make it shine again, the things that i want to upgrade is my gpu, psu, and cpu. Now i have a g2020 paired with a gt630 from inno3d on a h61 motherboard from ecs and a generic 300 watt psu. Guys please tell me what to upgrade to and i dont mind buying second or third hand parts, Thanks.
Ps. i just wanna play gta 5 on buttery smooth 30-60 fps no stuttering .

 

[SPgamer007]

I5 4460
ASrock H97
G.skill 4X2 gb(8gb) Ram
550W tier 1 PSU
GTX 970/R9 390

1080p built.

If you are NOT OK with the overall Price of the above build,you can replace to a gtx 960/R9 380 there from gtx 970/R9 390.
I5 4460 is the CPU you should upgrade to,nothing less.

 

[Tzn]

if you want cheap go i3 and gtx 750ti 2gb(btw it works wonders), if you have the money then a i5 and R9 380 4gb.