Most Cruise Ships now have allocated spaces for the Crew. In Disney, thay even have a pool for the Crew. Of course, it may not be an olympic-size thing, but enough for you to take a dip and cool off. As for the clothes, well ... it depends if you're lazy to wash your clothes weekly. Clothes enough for 1 - 2 weeks would suffice. Normally, Crew get to go out shopping for T-shirts, Polo Shirts, shorts ; etc. You probably might end up bringing home more purchased clothes than what you originally brought with you. hahahaha!!!!
first choose the clothes for the actual weather that you will be working on...
and do not take to much clothes!!! just enought for 1 month, and most confortable clothes.
You've picked a GREAT company to work for and a good department.
Carnival are renowned as being one of the most easy-going companies on the high seas. And I can vouch for that.
As casino you are a STAFF member and have quite a few privileges including being able to sun-bath in passenger areas (providing it's not around the immediate main pool area). And more than likely (depending on the ship) there'll be an optional sunbathing area for crew only.
You'll also have use of passenger facilities including the gym, sauna, etc. The only (understandable) rule is that the passengers ALWAYS have first priority over their facilities.
Regarding what to take... it doesn't matter what we tell you, you're going to take too much stuff! But you really only need the minimum of clothes. A few smart casual things for the crew bar (a couple of jeans, t-shirts, etc) and being a Carnival ship you're more than likely going somewhere hot so a couple of pairs of shorts and beachwear. Trust me, you'll come home with a lot more things (including new clothes) than you take - so do your best to be disciplined when packing (woman seem to find this a MUCH more difficult task than men!)