Rubies are in game currency. They just seem to be to encourage micro transactions. The problem with them is that there isn't much worth purchasing with these. Other than the streak protection, the rest of the options are a waste of time. As for the leader boards. Once you get to 100+ points per move, all you need to do is decrease your interval and farm the points. Pretty soon you will be getting huge amounts of points and shoot up the leader board. This defeats the purpose of learning. I often see people on one course in the multi millions in points and this is how they do it. I use to look at the leader boards but now ignore them because I know how to manipulate them. A simple solution is that you can't get more than 100 pts max, or perhaps reduce the amount of points if they decrease the spaced repetition to less than a week.