Well, what are you offering that other guilds aren't?
I mean, most other guilds are less exclusive and have an established active memberbase. Those are some pretty significant advantages so you're going to need something special to convince people to join your guild over the others.
By the time someone hits 5* they're obviously going to have a load of connections with players and 99%
will have a Guild and mates in that Guild whose stuck with them since the 2*'s.
Hope you like either anti-socials or douches that've got kicked out of their previous Guilds.