So I want beginning mages/learning new spells to show they're dangerous, difficult, and new.

For example:
Inefficient.
Chance for failing to cast.
Overdrawing mana in casting.
Damaging player.

The more you cast, the better spellcaster you are.
The more you cast a spell, the better you know it.
The less you know a spell, the more likely you are to bugger it and hurt yourself.


Types of failure:
Draw more mana than needed. (Two routes from here: Mana ups power on random element(s) or is just wasted. Mana overdraw leads to losing health, remember)
Spell just fizzles.
Spell explodes...in your face! Ouch.
Summon a demon.


Conditions, curses, modifiers, etc, can impact your spellcasting chance. Summoning a demon to wreak havoc, for example, is a worst case scenario. You got hexed, used a cursed -9001 wand of self-buggery, tried to cast a level 101 spell at level 1, and tried to crank up the power on the spell manually. Doom and gloom, boys and girls. Doom and gloom.


Don't forget about mana crystals or other objects storing your excess mana, and letting you draw from them.