Meet the requirement for Expert spells (75 skill level, easily obtainable within... ten or so levels), proceed to kick ass. What's the problem?
The last mage character I played was in his upper teens and his destruction skill wasn't that high. And he used only destruction for damage. Don't see how you get it in 10 or so levels.
I have tried to play a mage several different times now and unfortunately it is the lack of access to new spells that completely defeats me everytime. I don't want to play 80 hours on a character using the same handful of spells over and over. The fact that shopkeepers won't even sell them to you until you are skilled is even more ludicrous. I don't even know if the high level spells will be worth all the effort it takes to get there.
Magic and mages in general are by far my biggest complaint about Skyrim. I have shelved my pure mage characters until mods come out to put some "magic" back in the world.
This is a problem. If I remember correctly you could get high level spells in OB no matter what your skill level was (like the enemies explode spell from one of the mages guilds). You might not be able to use it because your magicka was too low, but you could buy it at least. Why not have some vendors sell higher level spells instead of only having spells based on your level.
This.
And don't forget to enchant some cost reduction gear.
Spend one or two hours grinding your enchantment skill to the point where you can craft at least 50% reduction so that you have a chance at casting enough destruction spells to actually kill things without running around in circles while your magicka regenerates at 1/3th of the normal rate.
(100% magicka regeneration becomes 33% in combat, 300% becomes 100%)
Of course, the WISEST thing you could do is to simply grind enchantment to the 80s right off the bat, and create 100% reduction for destruction, and never level magicka at all.
When you get 100% reduction, that 250 magicka pool feels like a waste when you could've spent 150 points on health instead.)
Yeah, grinding is exactly what I want to do to have a mage character. And if you grind your enchant to 80 "off the bat" won't you still have novice/apprentice spells with destruction in 20's-30's as you face higher level enemies? Sure, you won't be "running around in circles while your magicka regenerates at 1/3th of the normal rate", but you will be running around in circles while you flames does next to useless damage against higher level foes.