On our first Alaskan cruise, we way overpacked - I brought everything I thought I *might* need, and then some. I had long underwear & multiple sweaters which were never used. The second time we went back, we did better, but still took too much. The key really is in clothes that you can layer and take on/off as needed depending on the day. Jeans/pants + a t-shirt is my base outfit, with a fleece jacket as my first outer layer, then a waterproof shell to add if necessary. I also bring one "indoor" sweater to use in the dining rooms or theatres because I find them cold. Gloves/hat were only needed on Tracy Arm day, but definitely appreciated and didn't take too much space in luggage. I only bring 2 pairs of shoes - the ones I wear most of the time (just sneakers) and a pair of dressy sandals for dinners. Remember that you can do laundry on the ship, so don't bring too many doubles of any of the big bulky stuff - plus, since you don't sweat as much in a colder climate like Alaska, you can wear clothes more than once before they need to be washed.
Don't forget your binoculars and camera!
Aby