How much data do you plan on storing? If you’re going to stay under a couple terabytes then you could get away with one of the Bmax or GMKtek mini PCs for under a couple hundred bucks. They’re silent, decent amount of RAM, often have a slot for a second SSD and they’re tiny enough to throw anywhere.
I myself have one being delivered today, but on Amazon there’s a GMKtek mini PC with an Intel N150, 16GB RAM and 1TB SSD on sale for $195. Plex and Jellyfin support the Intel Quicksync engine for transcoding and you can fit several containers/apps in 16GB
If you grow out if it down the road then you’ll have a good idea by then what hardware you need to upgrade to.
The question is how motivated are you to learn what you need to manage a device?
If you want to dive in and get your hands dirty then I’d recommend a little mini PC off Amazon and Fedora Server which comes out of the box with Cockpit which will help you administer your server. If it’s something you’re not that into and just need storage for your stuff, I’d say pick up a NAS from someone like Synology or Ugreen. They’ll generally take care of themselves.