When a new Mon is born, it starts out at level 1 with no experience. It is up to you to help them reach their full potential, whether by battling to gain EXP or using items to speed up their progress (e.g., EXP Potions, Level Stones).
You can increase your Mon’s stats in 3 ways:
Gain enough experience points through battles to level up. Your Mon’s battle stats will increase by either 3, 6, or 9 attribute points. This depends on the growth trajectory of your Mon, which you can learn from its profile in the Mon encyclopedia.
Collect and combine all 3 Booster Shard shapes from the same stone to permanently increase the associated attribute by 1 point.
Transform your Mon to a higher-level form, resetting its base stats within higher ranges and also giving it a higher growth trajectory.
Both Mons engaging in a battle will gain EXP, whether they win or lose. However, winning a match always awards more EXP than losing a match. The amount awarded to each Mon is determined in proportion to the level difference between them.
For example, if a lower level Mon beats a higher level Mon, it will gain more EXP than its defeated higher level opponent — the greater the level difference, the greater amount of EXP gained. The opposite is true for the higher level losing Mon — a greater level difference means less EXP gained.
To level up, Mons must gain enough EXP to pass the required threshold for the next level — information which can be found in the Mon encyclopedia.
The following table will give you an idea of how much EXP it takes to advance your Mon to the next level. Notice that difficulty increases at higher levels.
The "EXP gain per win" andthe number of "Wins until next level" are only approximations, assuming that you are battling mons at exactly the same level. EXP gain and the number of wins will very likely vary, but we hope you find this reference helpful as a general estimate.