The girls have to find two more members before they can be an official club, but Bansei holds a monopoly on the serious players.  It is time to track down old friends and rebuild Achiga’s Mahjong Club!
before you can become a club"?
con el mismo interés, 
antes de formar un club"?
de un grupo con intereses similares, si quieres formar un club, ¿no?
puisse devenir un vrai club ?
prima di poter diventare un club?