Is gains in the Destruction skill based on how much damage the spell does, or it's "expertise" level? Like, will a continously casted Flames spell give more gains per Magicka Bar or Monster than a spammed Firebolt, for instance? My new Lvl 8 or so Argonian Mage is at 40 something Destruction, and it's a pain in the ass to gain, especially with how slow Magicka regenerates in combat.

According to the UESP:

"Casting higher level spells gives generally faster skill increases (Novice