Gacha Club MP Booster and unit list
This Gacha Club active skill is called MP booster. This ability is actually one of the best in the game. Using this restores MP which allows other party members to use more skills. When this skill is maxed out it restores a ton of MP. If you want to beat Gacha Club bosses in a single fight then this skill is absolutely essential, possibly even two units with this skill.
The level progression of MP booster in Gacha Club is as follows:
Level 1: Gain 20 MP and +1MP speed
Level 2: Gain 25 MP and +1MP speed
Level 3: Gain 30 MP and +1MP speed
Level 4: Gain 35 MP and +1MP speed
Level 5: Gain 40 MP and +1MP speed
Here's a list of all Gacha Club Units that have MP Booster as their active skill: