Most likely it will be hot where you go. Pack light weight clothes to mix and match colors so you don't overpack. Also, a lightweight jacket or sweatshirt for some evening entertainment on the deck. I bring my own beach towel for on or off shore use. (If you lose the ships towel you will be charged). Don't forget your elegant night wear. Don't like the name scare you business casual is formal enough. I bring hangers because they never give you enough. Also, a battery operated clock so you know what time it is and a wristwatch for when you are not in the room. (I shut my phone off) I also bring rain ponchos. (you can purchase at the dollar store). Bringing your own drink cup is helpful so you don't have to keep refilling those small cups on the ship. Its also good to have when you are laying in the sun or enjoying deck entertainment. I hope that helps a little. I will be going again next month and have to say there is never a bad cruise!
The post office has boxes available in multiple sizes that will ship for a flat fee, regardless of weight. If you do not intend to spend your cruise time doing laundry, use a tight, sealable bag -- the type that you can squeeze the air out of -- as your dirty clothes bag (this is perfect for underwear). When that bag is becoming full, squeeze out the air and put it in the box. Mail that box to your home at the next port. (Remember to pack enough undies!) You now have room in your luggage for purchased items and your bag will not go over a weight limit.