Question Upgrading advice ($1k) CPU, MB, Case, Cooling

Feb 17, 2019
I'm relatively new to the PC building, I did it in high school as part of a project, but am green when it comes to handling my first round of upgrades.
The PC I built was a cookie cutter that I had been recommended and after attempting the research myself I'm drowned in the potential options and was hoping to find guidance here.

This is my current setup (I have a GeForce GTX 1080 now)
I'll keep it short and concise:
I have no time constraint or deadline, I use my PC mainly for gaming. I've started to branch out in titles a bit and with my tax return was hoping to invest in some upgrades.
I'm working with $~1k and am looking to upgrade my CPU, Motherboard, case and cooling (potentially RAM if deemed necessary). Essentially everything that's not my GPU or my power supply.

I already have all the peripherals and software I need so I'm only in the market for components. I'm using this monitor. I don't have a preference on any websites or brands but as far as I'm aware Intel makes the best CPUs (though I could be wrong).
I just want the best I can get in my price range. I care for function over form, as long as it works I don't need crazy RGB or a fish-tank water-cooler.

Thanks so much in advance and I apologize for my lack of knowledge on this subject but I'm willing to learn!