I believe Maths is not the best subject for GBL for the game-play most of the time is not part of the learning experience. Is it therefore really necessary to deliver the content in a game. Does that develop students’ understanding of the topic better compared to a more traditional approach?
I do use games however to develop literacy amongst my students. I like http://www.philologus.co.uk/ which you can use to create anagrams in seconds (nice starter) or a game of hangman (plenary?). It has various other options too. What I like about it is that it takes only a very short amount of time to create the game suitable for that particular lesson.