Should I Upgrade GPU or CPU

I built a $500 budget pc back in May and i do have too say its great for the price too performance ratio, but it barely does the job for me in the games im playing lately. I have a R7 265 paired with an FX-6300. Now i want to either upgrade my GPU(to get better performance in games) or my CPU since im starting to get into making "games" in Unity and look to make small web browser games in the future. Im looking to upgrade my GPU too a 970 but i think its too expensive and overkill for my budget. Any recommendation and opinions are welcome on this post.

Link to my build: https://pcpartpicker.com/b/JYP6Mp

A GPU will always give you more performance in games. CPU may but not that much. The only CPU upgrade option for you would be an 8350 but I wouldn't trust it on that motherboard and even then it won't change you single core performance so single threaded games won't run that well. So you'd have to go Intel which will be quite a bit of money and in game you will largely see no change.

Making little browser games doesn't require much CPU power anyway. The 6300 will be fine for that.

Get a new GPU. A 285 280X or R9 290 are all very good and can be had really cheaply right now. 

These GPU's will be good in games like Dayz, Arma 3, Skyrim (heavily modded with ENBs)?

Id say go for a new gpu. The fx 6300 will not bottleneck you unless your running sli/Crossfire on higher end cards. If you are gaming at 1440/1080 get nvidia. If at 4k go amd.

290x+8350<$500

Yes. They should give you a performance boost. All those games though, especially DayZ, are CPU intensive and poorly optimized for multiple threads and will therefore suffer on AMD CPUs. You'll see an increase in FPS but not as much or as stable as if you went with an Intel CPU.

test your pc with an emulator like dolphin or pcsx2 in software mode and again in dx11 max settings. then upgrade the part thats at 100%. keep in mind dolphin can only use 2 or 3 cores.

odds are if your pc can run them at full speed at max settings then it should be able to handle any game you create in unity. considering it has many of the same restrictions.

that said after looking at the specs for your mobo you may want to upgrade it first. then get an FX-9590. right now isn't really a good time to buy a new gpu with DX12 & the AMD 300 series around the corner.

Wouldn't it be the other way round?

The 290/290x have higher memory bandwidth and as such higher fps are obtainable at higher resolutions. Not to mention, the 390x and 380x are around the corner of which will steal the GPU crown. I don't even think a 980 ti will outperform them (when it launches).

Why a 9590? Why not oc an 8320?

The 290x outperforms the 780 in 4k most of the time. The 780ti Is better than the 780 but the 290x still holds decently against it. The 8gb 290x by saphire Can beat the 970 in 4k.  At 1080/1440 nvidia does outperform amd when on directx.

i hope that amd decides to make the 380-390x standard with 8GB of ram.

on the poor little matx mobo

because you're never going to get a 8320 to 5ghz.

That said, a 9590 on OP's current motherboard would be really bad.