Actually, there is no 'best clan'. It depends on your own opinion, and it depends on what is a good clan in your vision (strength in CTF, strength in battle, fun, friendships/atmosphere, activity, attitude of the members etc.). You can also judge a clan on how long it exists, how many members it has, how good the hotel is the leader has built (cough). You should explore the world of clans in JJ2 and then decide yourself which one you like most and suits your own style.