Each cruise is different. On our most recent, there were only 9 cabins participating. We did a sign up on the cruise meets section and closed it about a week before sailing. We also specified that gifts were to be minimal in expense, and focus on creativity. I've read of groups that did a price limit--we didn't specify, but only said "not costly." Each cabin was expected to give at least once, but certainly not every day. Most of us counted people--kids and adults separately...but some did "cabin" gifts.
Items included....Postcard of Magic in port, stickers, individually wrapped candies, pens/pencils, drink cup (small size, nice for excursions), magnets, Disney character note pad, "princess" bracelet, pirate tattoos, pirate eye patches, etc.
To keep it inexpensive, think dollar stores, things that come in bulk packages.....after Halloween sales (for pirate stuff). Like a package of 10 pencils might be $1 or $2. Anything with a pirate, ocean, or Disney theme works well.