Making a FB group = Managing a teamwork = being a Leader...
So, the most important thing to wonder : What are your goals and perspectives (what you want to do with this group) ?
In general, Groups of FB are here to make actions and/or to share a common information for people who recognize each others...
But, for fun and general informations, FB pages can make the deal...
So, think on what you want from this mass of people to achieve after a period of time and be sure to make a progressive common goal that gathers them and makes them engaged to participate at each connection...
Joke : In my country this common goal is "being like Japan"... So, Good Luck for you Japenese