Dresses with delicate embellishments like sequins, beading, or lace need extra care when being transported, but carrying a garment bag in addition to your luggage is a pain.
Use tissue paper to protect your dress so you can pack it in your suitcase.
The tissue paper keeps other clothes in your bag from rubbing against the dress and causing the sequins or beading to fall off.
It also protects your other clothes from dresses with glitter or other sticky embellishments.
Spread out a layer of tissue paper, then lay down your dress, then another layer of tissue.
Roll the whole thing together so you can easily fit the dress into your suitcase.