Another good bet would be to find people in game that you enjoy playing with. Get them on your friends list and get to know them a bit more. Then when you sort out what your clan is going to be, invite them to be a part of it. If they aren't affiliated with anyone (a lot of people aren't), and also enjoy playing with you, they're more likely to tag along. The game is much better when you can regularly play with good people, so everyone wins.
I think the majority of the clans in this game didn't actually migrate to here from other games, but instead started locally just by revolving around people that enjoy playing with each other.
Good luck with the clan formation!