for white items (normal, superior, not sure about cracked), lazuk would give the max socket allow for the item for that quality level (I think). Arreats summit is down right now, so I don't remember how many socket is max for myth sword. But for example, a white cb would give 6 socket, cs would give 5, cryptic axe = 5 etc. Magic items would recieve 1 or 2 sockets randomly. Unique, set, rare would received 1 socket. You cannot use the quest on something that has socket already.
PS. I wouldn't bother trying to sell such an item. You would have an easier time selling many other things for a soj.