Buildapc

Memory seems like an easy win, but it's really about what are you currently limited by?

So in your most used application, or game, what is your current bottleneck?

Is your memory mostly used? Is your CPU high? Are you getting thermally throttled? Is your disc thrashing?

Profiling your main use case, will let you know what you want to improve, give you the easy wins. Cuz you could easily upgrade anything in your system right now, but you may not notice any improvement depending on your use case

You don't list your storage here, I don't know what you're currently using, but if NVMe make sense for you, that might improve load times

Pretty sure that motherboard is only gen 3 pcie, so you aren't getting full potential of your gpu. Bumping to a b520/b550 would help there.

16gb of ram is fine, but 32gb would likely work better with newer games.

I'd invest in a better power supply down the line. At least something gold+ is my usual recommendation.

CPU should be fine, even with the most modern games. Cooler is a beast. GPU is a little on the lower side of you're looking at 1440 resolution, but should be golden for 1080.

The motherboard is by far the weakest point, and is likely holding back other parts of the build already.

The MB is weak for gen3 PCIe. That's likely not even 5% loss of GPU performance. It's a mistake. But, it doesn't seem worth the money to fix unless there's also other reasons.

If you've trimmed the fat and still are running low on RAM then it's the priority. Page file usage always kills performance. If you're not running low then an upgrade does nothing.

I've a low risk tolerance with my desktop rig. My next upgrades would be a Gold PSU and line interrupt UPS.