>>527496908
IDK about best, but currently I'm experimenting with:
Elda (abyss 3 progression)
Barbara, Ophelia and Valdor for strong disciplines
Benjamin, Clarissa for high BP and favored boons (In order, Strength and Luck)

class changes are unreliable and you shouldn't think about it too much until you have it show up in your shop. for the case of gandolfo the SP saving passive isn't very strong because we can farm SP restoration potions that gives 25 SP per usage, in addition to not scaling with higher skill levels