You didn't say how long a cruise and how many people, but let's assume 2 people for 7 days.
We need a 30 inch rolling one, a garment bag (with wheels) and a 20 inch rolling bag plus a tote. That should cover most everything.
The big secret with packing is mix and matching your clothes. I will only bring 3 pairs of pants, for instance, for a 7 night cruise.
Finally, we did the 15 night Hawaii cruise this January, but I just packed for 7 days and did laundry. Funny enough, I only needed to wash under clothes, socks, and daytime clothes. All the night stuff was still fresh.