I haven't been on a cruise, but I just got back from a Caribbean resort, and I think "elegant casual" is similar to resort evening dress code (ours called it "smart dress"). For the evenings when we had to dress up, I packed a summery fit-and-flare dress, cropped jacket, floaty midi skirt, boatneck knit top, nice sandals, and a couple of necklaces. Since your friend's cruise has eight such evenings, I'd pack two dresses and a variety of toppers and accessories, as you mention. (Cropped cardigan? Blazer in a summery or dressy fabric?) This link might help: http://www.cheapcaribbean.com/deals/cracking-dress-code.html