Each Cruise Line has it's own dress code. Ladies should dress equally formally or informally. If you don't like to dress up, there ara always ways around it. Be sure to bring any medications, sunblock, a camera, comfortable shoes, an a bathing suit. You will also need to bring enough money for tips and any purchases you might make.
Most ships have cashless payment systems for drinks, shore excursions , etc.
Let us know where you want to go and we will help you with your packing list.