It takes 114. something to not fizz on 7th Circle Spells, and basically 120 to never fizz on 8th circle spells. With that said, you WILL still fizz them if you are interrupted during casting. As was mentioned, make sure all of your armor is leather, or says "mage armor" on it if it's metal. Lower mana cost items reduce your cost of mana/spell, so get as much as you can...my mage's run with 40+%, which significantly reduces mana cost. Lower reg cost armor only reduces the reagents you need, it has no effect on your mana pool. Make sur you max your intelligence at 125, as that will increase your mana pool as well. Get your eval up as fast as you can too....that won't help your mana, but it does increase your spell damage, which should require fewer spells to kill something.

The stat increase after 6 months is a 5 point addition to your total stats or to a skill, your choice. Take the stat increase, as 5 points of skill won't mean squat in the long run.