So much of this is TL;DR but one tip I didn't happen to see is when you're levelling cards is best to do the ones only available in the Gacha first simply because if you're rolling in the exploration/GHQ slot machine and get one of the exploration girls that's already maxxed you only get a tiny amount of Pero (300 for N, 700 for R, 1500 for SR) while in the Gacha getting a girl you've already maxxed will level up another card of that rarity or (at a minuscule chance) a higher rarity card, a MUCH better deal.