Basically, によって being an active member of a club and contributing things which others like: 1. Getting the links, articles, 画像 and 動画 you've added fanned 2. Answering lots of questions, アンケー etc. 3. It's easier to get メダル in もっと見る active クラブ than dormant ones.
I don't think there's a set number of ファン または contributions. The system's pretty random. Sometimes it doesn't really make sense.
