All great suggestions, here is a few more for you: I always have a warm wrap, such as a sweater, hoodie, poncho, or pashmina type scarf. Usually if I’m packing minimally it would be a large scarf. Great for wearing on the airplane, on the beach for a towel or to sit on, if it rains or is exceptionally windy it adds protection, one time it was used to shelter a grandchild. It is almost ALWAYS chilly in the ships dining room, if not there somewhere else. Ships temperatures are not regulated.
Off board I always bring an unstructured backpack. Plus a bra friendly credit card sized holder for credit cards, ship card, ID. Yep, it goes in my bra.
Evening Shoes: Shoes make a difference in a look. I bring a pair of black embellished flats to wear every evening, including Gala nights. I don’t usually wear dresses, however if traveling with Europeans, and on Cunard where the standards are dressier, one or two little black dresses are packed.