So I’m running a sorc with full Tal set, and I just got the armor socketed.
The question is: What should I put in? Ith adds 15% dmg goes to mana which sounds intriguing for a low price, Sur adds +5% total mana, or maybe a certain jewel? Cold Rainbow facet? What do you say?
You shouldn’t be worrying about mana, as your merc should have an insight. Sur is a waste as … insight. A facet would be good, or you can UM it if you need the resists. Otherwise, I would just Ist it and enjoy the extra MF.
Either Um or Ist are your best options.
Ptopaz if you do not have those yet.
Why is this even question? Perfect Topaz obviously 
Ptopaz is the standard cheap option, can always upgrade from there
Yeah by 1% 
, i usualy dont do that tho, its waste of good rune.