So I finally picked up Kamihime, and have questions;

Does the currently available main story stop at #16 Meeting the Zestians?
Do Gems have any use outside the gach, and as an expense when limit breaking stuff?
Is there any way to grind out levels on souls/kamihime quickly? Kinda like the "Maruppe March" in xoverd.
Are "Idea Core" items used to limit break, or do they have another use? Gotten a few of them from doing raids.
I'm guessing from the raids I've done, that they're the best way to obtain the items for limit breaking?
On some of my Eidolons, in the bottom right corner of their boxes in orange text it has +1, +2, etc. What exactly is that?