@Liaely Don't overthink the hardware $$$. The "Servethehome" site has a bunch of articles under #ProjectTinyMiniMicro about repurposing super cheap corporate surplus desktop PC's as servers.
$$-wise, one of the best investments would really just be making sure you're using NVMe storage.
Tech-wise, get comfortable with #Docker and #DockerCompose.
Also get comfortable with a reverse proxy that you're going to get a lot of use out of. #Traefik and #nginx are really good ones that many tend to gravitate to.
#GoToSocial might be the easiest one to deploy. #Mastodon and #Pixelfed might be some of the hardest. #lemmy & #peerTube are somewhere in between in difficulty to set up.
I have some (non-enshittified / non-monetized) how-to's for deploying some #selfHosted services on Docker if it helps. magnus919.com blog.
But really just get very comfortable with Docker and your reverse proxy. If you do both of those things, the rest becomes a lot easier. Traefik has more of a learning curve maybe than nginx but scales up really nicely, so once you've got it figured out it is ridiculously easy to add more services to it and get https
"for free".