noob questions seeking non-noob answers

I've been interested in self hosting a small variety of services yet I'm so confused on where to start. What would you guys recommend for a server machine?

My main uses (and some of the services I think are appropriate for the use case) are:

• 1tb photo, video storage, push/pull (immich)
• 512gb total shared between downloaded music storage (navidrome) and pdf/ebook storage (calibre)—all pull only
• 1tb movies/tv storage on a media server (jellyfin)
• 512gb storage for random junk or whatever, plus a file transfer push/pull (syncthing..? or nextcloud?)
• potential basic bio website hosting (near future)
• potential email hosting (distant future)

anyways with that all said i have a few questions:

• what server should i buy if i want to expand storage in the future? should i just build a pc with like 3x1tb storage, or 6x1tb storage w/ redundancy? totally confused about the concept of redundancy lol
• any thoughts on the services im suggesting? especially for file transfer