Tagging this with gameplay_mechanics because Kidian's normal skill gains additional hits for each piece of equipment she's wearing, and the cardboard box, elven wand, and tiara are three of the cheapest items in the game, so just dressing her in cheap crap is an effective way of scaling her damage. The actual effects of the items aren't relevant compared to the extra hits she gains just by wearing them.

@IndustriousMechanic said in comment #2589195:

The cardboard box, elven wand, and tiara are three of the cheapest items in the game, so just dressing her in cheap crap is an effective way of scaling her damage. The actual effects of the items aren't relevant compared to the extra hits she gains just by wearing them.

I'd say the elven wand and kunai is pretty good, tiara is so so (she can't benefit from it on her own) and the cardboard box is overshadowed by the crown of thorns. It is only 1 coin more and it gives skill damage in addition to the def. Also rusty awl is actually the cheapest item but I don't see you mention it