Another recommend for build it yourself. I saw deals on 8tb drives at my local micro center and through 2 into an old desktop I no longer used. Been running that with TrueNas scale for a little over a year and its been great. I did recently switch to Ubuntu server after some docker issues that were specific to truenas though. Honestly given the budget you mentioned, a cheaper minipc off amazon and an external drive or 2 is a good place to start off. Its nothing crazy but you'll have something functional to see what you need and want out of a server.