My current character has almost run his course. He was a high-elf that I morphed into a really great thief/assasin/archer. He almost never uses magicka but I chose a high-elf because of their magicka. I wanted it was a last resort.

But this next one I want to be different. The problem is, that the thieves and assassin quests seem anathema to a pure magick-user. When I picture a character like Gandolf or Merlin, I don't picture them sneaking around stabbing bad guys in the back while sporting leather armor. It's all about the robes. So that part of the game might not be as fun; oh well.

But I've never played this type of character. Not in Skyrim or Morrowind. I've always been drawn to the stealthy characters. But now I want to do something completely different.

The priorities would seem to be as follows:

1. Destruction: you gotta kill the bad guys
2. Alteration: without protection the bad guys will kill you

But then what? If anyone here would give me a rundown on how they've gone about creating pure mage characters and their aspects I'd appreciate it. Thanks!

1. Level the magic tree.
2. Enchant equip for zero cost destruction cost.
3. Kill bad guys.

The way I played pure mage, I added sneak to it so it wasn't quite as pure.

If you don't want to do that, it would be possible, but you would have trouble at low level, and you would want to grind illusion and conjuration probably. I would look out for conjuration staffs. Maybe do a certain drinking booze quest early on. You need ways to break aggro other than sneak, basically.

Using robes for a mage is beneficial if you don't want to melee. You need loads of magicka unless you really really grind enchanting, and personally I think it is better to just put the points into magicka anyway and not worry so much about enchanting.

This is one traditional approach but there are others. My choice is Destruction and Conjuration, robes only and no ironskin or the like.
The idea is high damage with summons (and maybe Lydia) to divert attention from melee types. The thing is just not to get hit. Mages are no problem with a Breton/Atronach build, they just replenish your magicka until you get 0 cost casting.
This sort of build only requires points in three schools; destruction, conjuration and enchanting. You can develop other skills for your amusemant but they aren't necessary.
I like minimal low level builds and this one can top out at only level 22-24 if you're strict about it. Just MHO, of course.