Memoria can earn experience by sacrificing other memoria. By leveling up a memoria, its stat bonuses will increase. The experience curve is the same across different rarity, but higher rarity allows higher maximum level.
Each copy of a memoria gives by default 100 EXP per its rarity level and is influenced by its level and in case of 3* and 4*, using dupes; occasionally it results in super successful, which gives 50% more experience, or more rarely, ultra successful, which gives 100% more. The probability of the bonus is not known for now.
Each memoria starts with a base level of 10, 15, 20 or 30 depending on its rarity; Limit Breaking memoria increases the cap by 5 each, up to 20 more levels and gives more EXP than normally.