Well I have been a member of both a Clan and a Coven, and of the two I'd recommend the Clan. More free spirited and less confining.
My Coven was a group I joined in college, we were just messing around really. You could tell how serious about the whole thing we were, there were only nine of us and we never bothered looking for more people to join us. I now know covens function quite well on less than thirteen, but I didn't know then. I think we all thought we had to have thirteen to have the spells and things work, and still didn't bother recruiting more members. I miss those days.

It's a great shame, but once we got a serious member who 'organised' us all into a proper coven of thirteen, and started doing things properly, structuring spells and sabbats, things began to change, the group dynamic altered drastically and after a while we all just kind of drifted away to other things.
I keep in touch with a couple of them, but not regularly and neither of them still practice at all.
My Clan was a thing I started with a few others I met in a nightclub, we met twice a week, before I had the children, and
we'd go out one night to a club or a party together, and the other night we'd meet at one or other of our houses and just talk, about anything and everything to do with Vampires. We'd order Pizza, with garlic, LOL and drink lager and just talk, about how it felt, what it meant, how we came to be where we were, and where we wanted to be in the future. It was just like a real family gathering, like the one I did with my parents every Sunday, but better. There were six of them and they became my second family and I still keep in close touch with all but one of them. One moved away and we all lost touch with her, it was like losing an arm.
Clans don't have to be big organised groups with ideas of world domination, they can be small intimate groups or families who feel a bond each toward the others. It's more than friendship and sometimes feels even more like family than the family I was born to. They are guides for my chidren, Aunty Jo and Uncle Taj, etc, (if I'd been christian they'd be called God parents) and are the people I can count on to be there if I need anything, help, advice, assistance, money, cheering up, bringing down to earth. They are honest and truthful, even when I don't want to hear it, and I don't even want to think of my life without them. They're my Clan and are almost as much a part of me as my children.