I'm going to disagree with "join an FC as soon as possible". Unlike LSs, you can only be in one. IMO, it's worth it to find that right one that fits really well. Yes, you can leave, but it's not quite as trivial of a deal as LSs. People spend a lot more time building the community of an FC (vs LS), and people will remember you.

Compare to an LS... most of them, people come and go pretty casually and there's less expectations in general. I'd say feel free to join (and in most cases, quit!) linkshells as you please. You can have up to 8 as well.