Just got me the Mundane Ring and be equipping on my character but I'm pretty confused here. It's effects are 35% reflect spell and 50% magic resistance. Does magic resistance mean I generally resist ALL magic? Does it include the elemental ones too like fire, ice, and shock? My frost and fire resistance are both 95% and my shock is 70%. If I take off my weatherward circlet (25% fire and frost) it'll go down to 70%, then equip my mundane ring, will that mean that my element resistances will go up to 120%?

I've always thought Resist Magic means all types of magic, wheras Resist Fire or Resist Shock only pertain to those elements. As for your 2nd question, I'm not sure. Somebody else will know the answer for sure.

The way thing are set I would hazard elemental resistence is counted last, and may, subtract from the % already decreased by resist magic..
So you may take 20 fire damage from a spell, resist 50% magic, resist 50% fire and take 5 damage??

This is based on what I know, that the defense system goes Reflect - Absorb - resist magic, and reckon it would just continue with - resist element.

Resist magicka will resist all hostile magic. With just the mundane ring, it's 50%. This means that half the effect of every bad spell is resisted. If it is damage health or fire for example, the damage is half. If it is a constant effect like silence or paralize, then the duration is halved.

I'm not very sure about the exact details/interface of having having resist magic and say, resist fire. Perhaps as Madocmayhem suggests?