Other than guilds, I found using manual match teams with few to little down time to give a decent amount of gems. Every match that the player makes by shifting a gem on the board gives a chance for a gold key, which gives the chance of gold, glory, or gems. Having a team that has a damage output of skulls only with a decent amount of gem spawning would be good. These types of teams are also more likely to get 7x cascades for maps. Abhorath is also a good unit to have for this build for his ability alone can sometimes give you a map due to the ridiculous cascade, or backfire horribly.