Everyone knows that in their spell list, they have their mana cost and proficiency.
Level 1: icicle 40 (15 mana)
Why haven't we implemented this with skills, at least for those skills that actually have a mana cost?
Level 15: camp 100 (20 mana)
Level 29: predict 100 (15 mana)
Etc.
Granted there's more skills in each class that don't than do, but it's handy to know from the outset.