Max MR

[WingedDog]

To notice:
MR effect stacks only for different items. You can't add 2 amulets of antimagic to one commander - you'll get effect only from 1, but if you give him amulet, lead shield, astral cap and rainbow armor - you'll get MR boost from every item.
Combat MR spells do not stack. IE: you can't cast resist magic and iron will on the same character to get a huge MR boost, you can cast only 1 spell.
MA, LA Ermor and LA C'tis have priest spells increasing MR, they also do not stack with combat magic spells.