Mage is really a glass cannon. You should save some scrolls to invest in your armor too. I typically aim for the highest tier I can get to within my strength requirements with a few scrolls. Like if I am dominating and have 6 or so scrolls, I can upgrade Tier5 armor to fit at str 15 (18-6*0.5). Otherwise I will accept tier4 and in a pinch tier3. Usually you can find tier2 or tier3 that fit by the time you have the strength for them.
Other tips:

• I save almost all my scrolls of identify to turn into scroll of divination up until I know every single potion and ring. Convert your unneeded seeds and potions into alchemy energy.
• Make big FU potions for the dwarven king fight. I do dragon blood and infernal brew to just light the arena on fire.
• If you are lucky enough to find a Ring of Wealth early - put ALL of your scrolls of upgrade into it. Trust me. Might be difficult on the mage though.