Helping expand and grow your FC just sounds like your after numbers, the quality of players is better than quantity. Say what some of your goals are or what activities you all do together eg raiding, events, pvp etc
the way my FC does it is we have a social LS and invite people to that who we meet in PF/DF or just randomly and who seem fun, social, helpful and are good players/people even if they are already in a FC. We get to know them and eventually they may decide to join if not they are still in the LS.
we have gone from around 12 to 50+ active members this way and everybody gets along