There is something weird about wands and i don't know if it's a bug or it's just how the game works.
I've upgraded my wand using a +12 cupon, but when I equip it, it doesn't change my stats at all. The only thing where I can tell that it does something is when i use the Spirit Rod attack, which increases the damage of it a lot (I suppose it applies to other wand skills too). It is strange because when I equip other stuff, such as gloves or armor, my stats change. I also don't know if it is just a wand thing or other sub weapons work the same.