We have bow, one handed, 2 handed weapons damage boost from armor via enchanting or get it from drops or even buy those from NPCs along with talent perks that boost damage up. For mage we have only perks that boost 50% damge for each elements. My character is lv70 and i never see any items that has spell damage boost for mage on armor. Does anyone ever see it on your journey?
Just a tip, to increase (double IIRC) the damage of fire destruction spells, you first need to get the flame perk which fears the enemy with fire magic. Then get the illusion spell that boosts fear effects, gives fire destruction a big boost.