1. Buy four Elemental Armour + Death Ward accessories, trading in our current rings.
You now have six upgrades worth of cash.Your new rings sort of resemble the old ones, copper circles with six gems set in the front, but these now have been shaped to look like a bat-shape twisted into a ring. The back side of the rings, opposite the front gems, contain a bit of purple cystal to round out the full set of protections.
Look into an MP-regen staff for Willis.
Willis, at this time, can't use a staff. He's gotta train to be able to use one first. Usually staffs do less damage than normal weapons, but they boost various elements of magic. Empower certain kinds of spells, for instance, or provide built-in spells that can be cast several times, or other magical abilities. About all they can't do is boost max MP.. for some reason that only seems to work on accessories. Although, maybe if you have an alchemical staff...
Mana regeneration on a staff is possible. The numbers don't look super good for Willis, though, being in the range of 3 or 4 mana a turn. That would be nice if he did cheap support spells or reasonably-priced healing, but he does big nasty spells that make all the people fall down, costing dozens of mana.
What does look more appealing is the possibility of getting even more damage on it. Or, alternatively, get a few charges of a high-powered spell added to a staff, so he can cast it without using his MP..