Hardware suggestions?

I'm looking into building my first dedicated home server. I've repurposed old laptops and desktops as servers in the past, but have never actually built a system specifically to be a good server, and I've never really used a server as anything more than a toy, if you know what I mean - I've set up a bunch of freebsd jails, or a zfs nas, or a bunch of VMs, but then I'll get bored and not actually use them. So I don't really know what hardware choices would be helpful and which wouldn't.

I'm aiming to use it for things like a pi-hole and backup storage (using zfs if that's feasible, maybe 4 drives, maybe 8TB each, is that feasible?). My partner is excited about the idea of a Plex server so I suppose the option to do that at some point in the future could be useful.

My budget for now is £1000, though it doesn't all have to be done at once. Is that plausible?