The spoilers are only about Shivering Isles http://www.uesp.net/wiki/Shivering:Shivering_Isles http://elderscrolls.wikia.com/wiki/The_Elder_Scrolls_IV:_Shivering_Isles.

Well my character

is level 39 ; she is a Breton Monk which I planned not to have her cast spells but ended as my most powerful caster. In one of the last mission of Shivering Isles main quest, I found a 33% damage reflection ring, I had found before a 33% amulet of the like plus a 6% ring. So those items are quite the game easer. I also have a setup for getting hit by magic, one for looting and another for exploring. At this point, the only real hassle in Oblivion is to change my equipment. Well to be fair, a reason I can change so much is as my character was a monk from the start and I played Morrowind, I knew about the Unarmored skill and thought it was quite appropriate for her so I used the mod http://planetelderscrolls.gamespy.com/View.php?view=OblivionMods.Detail&id=1956#Files which allow more freedom than if she was specialized in heavy armor.

So this game I was oriented toward quests because they're fun but mostly because they're increasing skills ; rather than raiding/adventuring/looting forts, ayelid ruins, mines & caves. Of course I'm assuming the vast majority player do daedric shrines quests, which give nice items. Well now seeing just how powerful wearable items can be, I'm not so sure I made the right choice. Perhaps after having access to the http://www.uesp.net/wiki/Oblivion:Enchanting apparatus and having a high enough Unarmored skill, I should have made luck attribute increasing clothes, to reach 100, then put serious effort in raiding.

The most important aspect of my game was spell absorption, because not only enemy magicians were not a threat but they were actually a source of power. Before going the "normal" way somewhere, I sneak to see if there's any mage or magical creature further on then I'd come back from the start playing revealed and I'd start using magic a bit before reaching my personal magic well. One of the funniest strategies was to send destruction balls/waves/hadoukens to melee enemies while avoiding them but at the same time keeping an eye on the magical enemy to know when something would be sent my way so I'd know if I should keep moving in the same direction or if I'd have the time to sop moving. So I'd avoid the melees while being replenished by magic while getting rid of the muscle thrash. Not only could I not start using magic a bit before the enemy magical creature or humanoid but I actually didn't kill him/her/it and kept the same tactic as long as possible. The best was magic "traps" which was in effect for my character not only a source of health but a way to increase her destruction skill.

So I didn't understand the importance of items and focused more on skills & attributes while I should have spent like 1/3 of the time looking for powerful items.