Log in for seven consecutive days to increase the daily rewards. On the second day, you will be given 50 gems. After gaining every two or three levels, you will be awarded a level plan pack. The packs contain resources, boosters, and gems. The amount of gems will increase the higher your level. Participate in special events to get gem rewards. Play the "Aims" side missions. After successful completion, you will be given a reward that often includes gems. There are three "Aims" categories: Basic, Military, And glory. Basic missions are generic, Military missions involve fighting other bases, and Glory missions are related to your own personal growth.