Can anyone help with this? I've got loads of gear with broken materia I've not bothered to restore yet, but I'm unsure how to go about it.

Vintage Kite Shield - IV
Cobalt Celata - III & IV
Sentinel's Gauntlets - IV & IV
Cobalt Sabatons - IV & IV
Cobalt Winglet HQ - IV & IV
Felt Trousers HQ - III, IV & IV
Cobalt Plate Belt HQ - IV & IV

It seems VIT is kind of useless on all of them (I think I got one to go +3, that's it), so any advice would be really appreciated.