I mean I personally use qum as a healing fountain to restore my party to full hp after battles, if one of my characters starts to run out of mana during trash fights I'll swap them out of the party.
The only time hp or mana healing items, outside of the orc fights where you lack a healer, were something I'd even think about, I had access to healing and yarra's mana recovery skills.
As for equipment I bought... 3 Buttplugs for Yarra Nalili and Riala, maybe a 4th for qum but I'd personally just steal someone else's if I felt qum was needed for a fight to counter debuffs, 1 Dirge Axe for Simon and Hilstara to share, At least 1 master staff for robin and altina to share, 1 Sylvan sword for Nalili, 1 Ardan Dirk for Aka, and maybe a Zirantian claw for Uyae(I think you can find 2 of those for free eventually, but Uyae could use one sooner than that). The armour you get for free is good enough for the most part, but better damage ends fights quicker.