Well, it depends on which cruise you'll be on; 3, 4 or 7 night.
However, I think it's safe to say you will need shorts, tops, khakis, bathing suit, sneakers/walking shoes, sandals, water shoes. A cocktail dress for formal/semi-formal night. Slacks will do for the other nights. Appropriate footwear for dinnner. Underwear. Sunblock. Deodorant. Toothbrush. Toothpaste.
I am being silly.
Resortwear for days and dinnerwear for nights.