First off, go to the Mystic Emporium shop in the Imperial City Market district.

Buy the spell that has the effect 'Weakness to Fire.'

For the next part, you either need to be in the Arcane University or have the Mage's Tower DLC. Create a spell that is 'Weakness to Fire', magnitude 3, duration 1 second on self.

From there, just stand next to a bed doing the quick spell glitch (If you don't know this, equip any weapon and any shield; hold block and keep casting a spell).

This levels up destruction at a reasonable speed, and if you do this somewhere safe, causes no damage whatsoever.