[Warhammer]

Short Answer: Alchemy

Long Answer:

I have a custom class called Warmage (copycat!), Breton, Antronach, level 65. All usefull skills at 100 so are all my attributes except luck.

Unboosted, I have about 500 manapoints, but still have about the same problem as you, since some og my favourite spells cost 120.

The solution, is... Alchemy.

Keeping in mind that:
1/ Spells of the same name are not cumulative but potions of the same name are.

2/ The higher your intelligence, the more powerfull the potions you make are.

So what you can do is make 50 fortify Intelligence potions, drink them all (hotkey helps), you can rise you intelligence to the thousands, and while it is so high you can make really powerfull potions, such as more fortify intelligence potions, restore magika,...

I have scores of potions that fortify intelligence by about 400 for 1000 seconds, that gives a huge mana reserve. Plus potions that restore Magika 60 points for 60 seconds, and so on.

At one points I had an intelligence of about 5,000 with a mana reserve of about 20,000 mana points, just for the fun of it.