Board Thread:Questions and Answers/@comment-85.244.16.235-20160109224217/@comment-27570299-20160111100845

By playing regularly you'll get your 50 stones to make a multi-summon every 2 weeks or so.

But after a while, you'll have finished the Quest mode, so no more stones from there. And also you'll have finished the Story/Strike events which come around frequently so no stones from there either. But that's already a lot of stones dude. By then you should have pretty strong teams !