We had our first ever cruise on Legend of The Seas 18 months ago and we found that you can wear anything you want. You can choose to be as dressy or casual as you like. Around the ship during the day people are walking around in anything from swimwear to casual trousrs and shirts. They do have dress code for the evenings for the main dining room. This included 3 -4 formal nights and several smart casual evenings. You can really go to town on the formal nights, with as much glitz and glam as you like, particularly on the second night which I think is the Captains evening. We took our two childen with us and they too loved dressing up in the diner jackets and evening dresses.
Hope you have a lovely time and you get out of it what you want to.