You can join as many as you want but you can only be a clan mate in 1 clan personally I see no point in being in more then 1 and as far as responsibilities I would say just get to know you other members and post things in your clan like new info Or things like that in my clan we have 200 but its split between Xbox systems and we have some who give mire effort then others but that lets the leaders know who they can depend on b4 the game comes out