I have multiple reservations about this gem system. It increases the need of books by a lot, I have 810 girls, and hundreds are at lvl 1 because I dont have enough books to level them up, now we will need books and 8 types of gems to reach the new girl level cap of 750? Does not look fun to me.
Also is it really necessary to create 8 types of gem? It would be a lot simpler to just make a gem awakening for all instead of one for each subtype , this will likely create multiple cases of too many of a type you don't need too little of on you do. It's a big unnecessary logics headache.