Playing as a straight-out mage is probably one of the easiest routes, just get one of the signs that gives you a big boost to magic. After a while, you just don't run out even after repeated spamming of the same overpowered spell--and you can kill most stuff in one or two shots.
Playing this way, you also have more control over leveling. I find that it helps to work on leveling your NON-CLASS skills instead of your class skills at first. Alchemy and Blacksmithing are definitely worth the effort to raise (and DON'T TAKE THEM AS CLASS SKILLS or you'll wind up at level 10 with no combat ability). Poison your weapons. Use stealth.
Staying out of range of the enemies and nailing them with spells or arrows is much more effective than trying to beat them at the game of attrition chicken that is called melee. And don't just run randomly through the countryside for no reason, the random encounters aren't worth it. Hit the towns and do all the silly side-quests--you'll pick up bits of nice gear and cash here and there without leveling. Once you get up in level, start hitting Oblivion gates for loot. (You can sprint through without fighting stuff if you want, they don't chase you very efficiently and once you grab the sphere from the spire you get teleported out.)