Someone probably has discovered it but I just found yesterday that you can get cost of using items to zero (0) by using:
- Robe of the Sublimate
Kayla from Stoutford
- Necklace of Dexterity
Pixtumn from the inn of Brimhaven (the guy who sells the suspicious dagger and gem in a quest)
- Ring of Dexterity (x2)
Teksin, the trader who failed to reach Remgard because he followed the wrong route(he sells Potion of Lightning attack)
- Feline gloves
Kayla from Stoutford
With these equipment, you can use any amount of item during combat. The downside is that you have to touch the End turn button everytime and your stats become low with these equipment.
I do not use this build because I am always using crits but you may find it good if you have a lot of money by using skills such as Treasure Hunter or Merchant as it really exploits the fact that you can use item infinitely
(PS: I read in many posts that Antison is trying different builds for fun, maybe you did not try this build yet?)