My FC helps people no matter what level they're. Just last week I dropped what I was doing to help a lv 15 find an npc. Most of our members are either friends from SW:TOR, friends of friends, wives, husbands or people who we've met on FF14 and played with before recruiting though. It's better to have a smaller sized FC(100 or lower) imo so that everyone gets to know each other, that way no one feels left out.

There are all different kinds of FCs out there. Probably lots that suit you. You just have to take the time to look.