I strongly recommend avoiding compiling thousands of dollars worth of gift cards. If you have to cancel or postpone the trip, you'll be stuck with all of your money on those cards, having to keep track of the numbers, having no choice but to spend the money on Disney, etc. Remember, everyone thinks they won't have to cancel their trip until they do have to cancel their trip.
Disney cruise pricing is based on school vacations. When it's easiest for kids to travel, the prices are much higher. Prices are lowest in mid-winter and in early fall, which is also hurricane season. The best way to save on
DCL is to cruise during these times of year.
There are some last-minute GT deals to be had, but keep in mind that you can't choose your stateroom with those. The last two times I booked GT to save money, I was assigned a handicapped stateroom with no bathtub, and the handicapped shower has no edge, so the whole bathroom floor gets soaked every time you shower. That might not be your cup of tea.
If you book via Costco Travel, or transfer your cruise to Costco Travel within 30 days of booking, you will get 10% of the base cruise cost back in the form of a Costco Shop Card that you can spend on goods at Costco, including gasoline at the pump. I've pumped months worth of free gasoline after sailing cruises booked via Costco. Costco's Visa card also gives 3% cash back (real cash, not Costco cash) for travel purchases.