Honestly, there is really no requirements for you to join other than you having to be active daily. You can even be a lv 1 and still join our league. We might however start screening members when we reach 20 members, so you might want to join as soon as possible if you want to get in since we are getting close to that mark.
I’m a lv. 148 FS, just applied to the league (IGN: Kaiser). I’m on everyday, and I’m down to do some league brawls. Although these days, I’m usually out of energy trying to farm for my 2nd CC and Helios Genesis =/