I love building my own systems too. My current desktop is a 2700X-based system that I built a year or two ago..
CPU :: AMD Ryzen 7 2700X 3.7 GHz 8-Core
CPU Cooler :: Corsair H115i PRO Water Cooler
MB :: Asus Crosshair VII Hero
Memory :: 32 GB (2 x 16 GB) DDR4-3200
HD :: WD Black 500 GB M.2 NVME SSD
GPU :: Radeon RX480 8 GB
Case :: Corsair Carbide 600Q Full Tower
PSU :: EVGA SuperNOVA T2 850 W 80+ Titanium Fully Modular
OS is currently Ubuntu 19.10 "Eoan Ermine". I can't really recommend Ubuntu these days, but Linux itself works great for both (sw dev) work and games. (Among other things I'm an occasional Minecraft player, hardcore Kerbal Space Program addict, and lately I've been getting back into Cities: Skylines.. via Steam no less.) I've also had Manjaro on it in the past and I might go back to that if Ubuntu continues to annoy me.
The cooler, GPU, case, and PSU are from a previous build. That was an AMD FX-8370 system which I overclocked so the cooler and PSU made more sense there. For this system I'm only pulling about 400W so they're currently overkill, but the parts you already have are cheap. The cooler and case make this a very quiet system too. If I really push it I can get some fan noise going but usually it is totally quiet. Someday I'll probably overclock this system too so the heat/noise/power headroom is handy to have in reserve.
I want to upgrade the GPU, but they're expensive and the RX 480 is (still) quite serviceable. I'd have to spend quite a lot more $$ than I'm willing to part with to get a decent enough performance jump to make it worth the trouble. I'd also like a bump in memory speed but again price is still a deterrent. Needs vs. wants and all that. This system - plus an upgrade or two as above - will probably keep me going for another couple years.
I do all my initial build planning on pcpartpicker so if you're -really- interested specs and convenient links are online there...
https://pcpartpicker.com/user/jmgrant/saved/drB6sY
edit: that 500G SSD might seem a bit small by today's standards but I forgot to mention that I netmount a 5TB partition from a nearby Synology NAS as my data drive ("D: drive" for you Windos users ) so the SSD is just for "C: drive" system/boot stuff and a couple active projects/games. The NAS is where I put all my video, pictures, music, documents, etc.
edit 2: I also built my brother a (much cheaper) system for his birthday last year. If I had it to do over I'd put in one of the newer APUs instead of the 2200G since one of the first things he wanted to do was upgrade the GPU/GFX for gaming. I think with a more recent APU that wouldn't be necessary, Do note that the case & MB support a full-sized GFX card if such an upgrade ever does become necessary/desirable and you want to get started with a minimum of $$$ outlay and upgrade later as funds become available. The AM4 socket (thanks AMD!) also supports upgrades all the way up to some of the Ryzen 7 CPUs as well. https://pcpartpicker.com/user/jmgrant/saved/pzsGf7