I see from your previous post, a dealer on the Glory? Did your hiring partner/specialist give you any info on that?
Looked at your run and see you have a lot of ports where you'll be able to buy pretty much anything you need . . .
But for the first few weeks, and until you get your first pay . . .
Find out what you need for your uniform - color of socks/shoes and anything else you can't get onboard/company doesn't supply. You might need formal wear, but you'll need to find out from Carnival specifically what.
Socks/underwear/cosmetics & toiletries for at LEAST two weeks. If you take any medications - at least a couple months and your script for more. If you're attached to specific shampoos/soaps/vitamins etc that may not be available in the States or Caribbean, you might want to bring - or have someone send them to you later.
For regular clothes - don't go too crazy bringing a lot of these. Jeans/long pants/shorts/a few shirts/swimsuit if you already have them. Fully shoes (sneakers/trainers) for off time on the ship as most companies will allow the crew to be wearing sandals or flip flops onboard. If you work out - bring those outfits.
Laptop or tablet a MUST. Download a bunch of current TV and Movies and you'll be immediately popular. External hard drive/thumb drives for trading music and video. Earphones!
Any photos or little things to remind you of home.
Ideally, get your luggage down to 1 big suitcase and 1 carry-on. You WILL be picking up a lot of stuff during your contract and will be buying another suitcase and bringing a lot home
I can't say enough how many stores there will be on your run that you can pick up pretty much anything else you need.
Check out Facebook for Carnival casino /crew groups.