Is there a minimum number of events in which I must participate?

No; however, participation is encouraged.  The more that a person participates the more likely it is that he or she will feel that he or she is a part of the organization.  It is also more likely that he or she will develop friendships.  It’s a totally different thing to shoot sporting clays with a bunch of strangers than it is to shoot with a bunch of friends, for example.