I started with a Dell Wyze 5070 from eBay. I put a 1Tb M2 sata in it, and 32Gb of RAM. Be warned it's really picky about RAM type. After a while I added 2 more, for testing and to spread the load a bit. I also added a proxmox backup server. I like the little boxes as they run at about 15W each.

If I was doing it again, I'd try and find a lowish power box that wasn't so picky on RAM, and also look at something with a 10GbE port so I could run ceph for some shared storage - but that pushed the price up...

HTH