I saw a post from about a month ago saying first place can get around 2500+ challenge stones a month.
Well I cleared every row for nearly a month and ended up with about 1600. Is it like level based?
Also, I was pretty positive at the end of the season you were given a certain amount of challenge stones. (This could be wrong seeing as this was my first csb). For some reason I really expected some though, maybe I saw a post on the forums or something.