The first dance trip teaches everyone the same lesson at roughly the same moment: usually around night three, when the shirts have run out and the shoes are still damp. Packing for a week of serious social dancing is a genuine skill, and getting it right is the difference between a glorious week and a soggy, blistered one.
Shoes come first, and you need at least two pairs. Dancing several hours a night soaks a pair through, and leather needs a full day to dry and recover its support. Alternating two pairs keeps both in good shape and saves your feet; a small brush and some talc for the soles round out the kit. This is not the corner to economise.
Then think about shirts and sweat. You will change once or twice a night, so pack more tops than feels sensible and lean towards fabrics that dry overnight on a balcony rail. A couple of quick-dry technical shirts earn their place even if they are not your most stylish; nobody remembers what you wore, but everybody remembers dancing with someone drenched.
The small things punch above their weight. Blister plasters, tape for hot spots, a refillable water bottle, magnesium if you cramp, and earplugs for the nights the room is louder than your ears would like. A dance holiday is an endurance event dressed up as a party, and treating your body accordingly means you are still dancing well on the last night, not limping through it.
Leave room for the reality that you will barely see the sights. The honest truth of a good dance week is that you sleep late, recover in the afternoon, and live at night. Pack for that life — comfortable days, well-supplied nights — rather than the sightseeing itinerary you will almost certainly abandon by Wednesday.