Sherry - raise and AW her asap. She is one of the better plat princesses that can buff your gold units.
Rachel - one of the best pirates even at DMM. Raise her ASAP. With the many pirate buffs in the future, Rachel will definitely benefit from them.
Zenobia - until you get Jerome, I'd say raise her as she can easily replace Phyllis as a soldier. Liselotte will also appear as an event unit in the future, so you will have a chance to obtain two plat soldiers.
Yuyu - I use her with Belinda for their high ATK and range increase. She also has higher ATK than most witches because of her elf race.
Bernice - your go-to heavy if you don't have any other higher rarity HAs
Kerry - same thing as Bernice.
Others
Betty and Monica - the former has gold get upon AW and the latter boosts DC drop. Whenever you have the time, try raising them as their drop increase percentage will increase after CC and AW.