Should I upgrade or completely rebuild my PC?

[datbubble]

Hello, I'll start pointing out my buget isn't really too high right now, hence why I'm asking if I should actually just upgrade a few components rather than buying a brand new PC.
I can already run a few games, which I play a lot, but most of them on the minimal settings, and there are some I'm afraid I can't even run at all without a significant performance loss.
I'd like to be able to crank some settings up to medium, high seems like a dream I cannot achieve at the moment due to a few personal priorities getting in the way. Anyways, my specs are

Intel Core i5-4460 CPU @ 3.20GHz
8GB RAM
NVIDIA GeForce GT 640
x64 Win8 OS

Am I missing anything?
Is it worth upgrading anything? Maybe my GPU is a bit weak? Or should I just wait and buy a new PC? Do not I'm not running the newest games like battlefield, etc. I mostly play stuff like Overwatch, GTA 5, Killing Floor 2, Guild Wars 2, and I was considering Black Desert Online.
But after seeing what those games look like without the minimum settings, I kinda feel like I'm missing out on a lot of details I would otherwise see with some better specs. What do you guys think?
Thanks in advance!

 

[timeconsumer]

Your CPU is fine for the next few years. What needs upgrading right now is your GPU. I don't know what your budget is, but something like a 750Ti or RX 460 would give you a nice performance boost for not a lot of money and you likely wouldn't need a new power supply.

Otherwise if you wanted to go bigger I'd want to know your PSU specs.

 

[datbubble]

I see. I remember before hearing about people buying components which they could not use for their PC. Is there a way of knowing if I can use that? Is it related to my motherboard?

 

[timeconsumer]

Your motherboard is fine. The only unknown here that we would need to know before really deciding what you can buy is your power supply specifications. But a cheap lightweight solution like a 750Ti and RX 460 can be run on even very low-end power supplies.