Is spamming your lowest lvl spell of a school the quickest way to lvl the skill?
 

Suppose I neglected by Evocation skill for like 40+ levels and want to train it up to 200+ from like 30. Is the quickest way to do that just spamming my lowest lvl / mana nuke on a mob 15-20 lvls lower me?

Or does spell level, mob level, or other things increase the skill up rate?

Doesn't apply to evocation (afaik - due to lack of appropriate clickies), but if you have a instaclicky version of a spell in your book you can quickly level up a skill by spamming that.

Like a SK levelling up by spamming grim aura on their sword of pain.

Does it have to be an instant clicky? I honestly can't say I have ever seen a skill gain from a clicky, but maybe I haven't been looking closely enough.

I have noticed Evocation will raise much faster than other casting skills, at least when being cast on monsters.

As for the original question, I believe (with no proof except anecdote) that casting higher level spells will indeed have a higher chance to raise the skill. However the obvious trade off being that higher level spells cost a lot more mana. I typically just spam the lowest mana spell I have as I find that faster over all.

This is a great question, and while I can't answer directly, what I do is just spam the lowest cost spell over and over. It definitely works!

Yes. Specifically because a fizzle still consumed a portion of the spell mana. So higher level spell means more mana consumed which means less casts vs the lower level spell.