Create leaderboards based on level of engagement

Leaderboards are a good gamification mechanism to increase retention and average time spent in app for existing users.

The most effective ones match players with similar levels of engagement, be they friends or strangers, as demonstrated by Zynga and Duolingo.

A leaderboard based strictly on friends is not as effective because few players have enough friends with a similar level of engagement. Many of their friends are inactive and those that are active are likely playing more or less than them.