I've been trying to make Gina work (her stats are too low and her level to increase is incredibly high). I've read from your posts that reading the sanctuary/ruins tablets/ lore boxes will grant her level but mine does not gain level from interacting with that lol.
The only thing I've invested on her is the 100k Self defense equippable book which enables her to use 1 skill and her other skills that are locked unless you have that book (magic that is okay for utility but damage is shit).
She has virtually no skills at all, and can only use weapon skills. Her level cap is 50 and each level up needs an ungodly amount of exp but each level up gives all her stats except for instinct a +15. Also, you need to interact with ALL the hexagon stones. ALL of them, it seems. The hexagon stones. At least the return is good enough.
And here's her equipment guide:
Leopard bicker (got from the goddess statue in the church right before fighting the last boss battle)
Guild saber JB (from the guild investigation questline. After you had a talk with Maya, talk to the receptionist again, the last option one, for the reward)
igarashi mail (the library at night's santuary)
self-defense book
Reaper medal (rare drop from the reaper right before the village chief boss)
flower brooch (got from the gentleman(lol) outside the village by getting him antique perfume gotten from the lady in front of the sushi shop at night by giving smoked bacon to her)