Norm has provided excellent advice in regard to the amount of clothing to pack and also in regard to what to pack for excursions to churches, cathedrals and mosques. I would also suggest that you pack a collapse able duffel bag for any additional purchases you will make while in the ports of the Mediterranean.
To save on packing resign yourself to the fact that you will have to send out some items to be laundered. It will save on weight, packing and the amount of luggage you will need. I feel it's worth the laundry charge. For a 14 day cruise we packed for a seven and sent out our laundry twice during the voyage. The charge was under $40. There are usually specials offered for regular items.
The number and weight of your luggage will be limited by the airlines and not the cruise line. The weight limit will be 50 to 70 lbs and 2 to 3 bags per person, depending on airline and class of travel.
Enjoy your cruise. The Mediterranean is a wonderful area and a favorite of mine.