While piefed.social is great so far, I would really like to start my own thing for several reasons. But I don't know where to begin and would like to join relevant communities before starting (for example, I heard there are Matrix servers for this, but haven't made the time to actively look for them yet).
Not yet, and probably not going to be able to allocate time for it in the next few months at least.
If I start an instance soon, it will almost certainly be through a managed service at first. Not letting perfect be the enemy of good and all that.
There's quite a learning curve if you're not familiar with self-hosting. Doing it through a managed service sounds like a good idea.