A new idea I thought would be good to add is 'Spell Card Mastery', which relates to the spells cards. This is when you accumulate experience for the used spell cards during battle, eventually becoming a 'Mastered Spell Card'.
Gaining experience: To gain experience for the Spell Card, you must use it in battle. For every time you use a Spell Card in battle, you gain 2 exp if successful or 1 exp if fizzles. If the damage Spell Cards used kills your enemy, you gain an extra 1 exp.
Spell Cards: Mastering Spell cards will only occur to School Cards. Any Spell Card bought with Trainer Points can earn experience too, but once those Spell Cards are removed and untrained, the experience becomes lost. Spell Cards from Equipment or Pets can't earn experience.
Mastering Cards: Mastering the spell cards will cause changes to occur on the spell card. This includes increased Accuracy and Damage for Damage Spell Cards, increased Healing for Healing Cards, increased Buffs from Buff Cards.