The most daunting thing for me about joining Mastodon/Fediverse was picking an instance.
Having joined one, a RL metaphor emerges for me: "it's like picking an apartment building."
You need to evaluate the management. Do they respect tenant rights? Is the desk clerk skeevy?
Do you want to live in a big impersonal complex? Or a little boarding house, where people share a lot and have house parties? You can even be a "home owner" and run your own instance (pay the bills, fix the plumbing).