Paulwem

Most officers do fine with a riding boot case (cloth is lightest) and a garment bag.
 
Suitcases that have room for both (integrated garment carriers, and big enough for the boots) would also work nicely as well, without being as heavy as the large cases we often use for hard armor costumes.

I just have a light garment bag for the tunic and pants.  For the boots and everything else, I have a large gym bag that everything goes in.  The boots are in some soft boot covers to protect them, a ziploc bag full of rank bars and the code cylinders, and then my belt rolls up into my hat.

I use a large 4 wheel suitcase. When transporting to a troop this allows space for drinks and food as well. 
 
It's surprising the amount of stuff that is required, to get the Admiral looking correct.