I have done so many cruises now I wouldnt change anything i do.
But looking back from the first cruise I would say I took too many clothes for dinner.
The following cruises I would wear the same skirt 2 or 3 times by changing my blouse or adding a sweater to cover a blouse I had worn before.
I only take one pair of black sandals to wear to dinner every night. They go with slacks, dresses or even a more formal dress, no need to pack 10 pairs of shoes like some ladies do. Of course i have my tennis shoes and thongs for walking to the pool
To save $$ on photos I often will take our camera and ask the photographers assistant to also take our photos with our camera, or DH would take mine and i take his. I only do this on Disney. They are great about it where other lines dont like to do this. I always buy the boarding photo.
If grandkids come I will buy more of their photos too but it does save a lot to have them use your camera too. Buying photos on board is expensive.
After having small items slide around the shelves in the bathroom I found its great to bring a cheap (dollar store) over the door shoe holder to put on the bathroom door. Then put things like tooth brushes, toothpaste, deodorant , make up, etc... In it. After the cruise just throw away the shoe holder and that makes room for souvenirs.