I generally tend to choose my race by my play style. Nords, Dark Elves, and Bretons all have some inborn resistance to at least one of the "Big three" magical killers. Bretons are restistant to magic in general, though it seems to be to a lesser degree. I've had luck with Nords, more luck with Dunmer and their built in flame cloak power, and I've really done well with this Breton.
I started off 25% magic resistant, right out of the gate. Then by becoming an agent of Mara, I added 15% more to that. That's 40% early on, which helps considerably with both mages and dragons. As I started finding/enchanting resistant garb, I was well on my way to the cap. I'm not sure if that's 80% or 85%, but I can walk right up to a dragon on full furnace mode, and not lose much health.