Hi, wanttocruisesomeday! We took an Alaskan cruise in May of this year, the first of what I hope will be many, as Alaska is just too big to see in one trip. I agree with the others who have said that Alaskan cruising takes a lot of planning and research. I suggest you start researching the ports and the types of tours that are available at each to see what might interest you. Each port will offer things that are very inexpensive. For instance in Juneau, you can hop on a shuttle bus and go to the Mendenhal Glacier on your own. No tour needed. The ports are small and quaint and very walkable. You will be able to find something to fit your budget.
Cruises early in the season and maybe late in the season are sometimes discounted. We got some good upgrades for very little on ours. Some of our cruise mates took the L.A. To Vancouver cruise and then did a back to back with the roundtrip Vancouver/Alaska portion. We chose the roundtrip rather than a one way due to time constraints. From my research, it seems that the trips out of Vancouver through the Inside Passage are highly recommended over the ones out of Seattle. We took the amtrack train from Seattle to Vancouver. It was indeed gorgeous scenery the entire trip.
If you are ever going to splurge on a balcony, Alaska is the place to do it. We splurged on an aft facing and wow, talk about a panoramic view! It was hard to tear myself away from the decks and windows to eat and sleep. A ship with a large forward viewing lounge would be ideal if you can't swing a balcony. Being out on deck is great, but it does get very chilly up there in Alaska!
I always say planning is almost as much fun as the trip. Enjoy!