Actually, mad god, I can count on when that mage would get seventh level spells -- by level seven or eight!
Just train in stonecraft or suncraft at the Wizard's Guild every time you go up a level. You can train a full level, without having to go through the skill point buildup necessary.
And I don't think the changing classes that you mentioned (while creating characters) counts toward the level issue. It's only leveling up in the game, and changing classes in the game, that makes the difference.
And Wyv, I think that formula is on the Best Tips thread...
