If you're good with medium/low settings for games at 1080p, you could go with the
ASRock A300W barebones kit (small case, motherboard, wifi, external power brick) $150
Ryzen 5 2400G (supposedly the wraith WILL fit in the A300W, if you take the shroud off) ~$140
Crucial MX500 SATA 2.5" SSD ~$130
HyperX 2x8GB 2933MHz RAM (the A300W uses LAPTOP memory) - HX429S17IB2K2 ~ $104
- $524 total
It's tiny - 155mm x 155mm x 80mm
(optionally the 3200Mhz RAM, HX432S20IB2K2 2x8 for $24 more)
I am guessing with how much storage you want/need, and I went with the 2.5" drive because, if you go with M.2, the M.2 supports NVMe ONLY. There's a QVL list for what's supported for M.2 drives, and while others work, it MIGHT be a gamble if you pick one not on the list.
If you don't need 16GB of RAM, you can get 2x4GB, and obviously that will drop the price some.
I have one of these, but I went super-low-end, getting 2x4GB 2400MHz (I stuck with the QVL list for RAM), and an Athlon 200GE CPU with a 128GB Patriot NVMe SSD (my previous system's install, which this one would replace, was in total under 30GB). My goal was Linux OS, and keep the TOTAL cost under $300. I use it to connect to work, do some web-browsing, Facebook, YouTube, etc., and retro gaming.
Keep in mind, this thing is so tiny because there is no PCIe slot!! You MUST use a Ryzen with integrated graphics! Ergo, no chance of upgrading to a better video card in the future.
EDIT: I also seem to recall a YouTube video where someone built one of these with 3200MHz RAM and it worked. Officially not supported, but you know how that goes.