Someone who's soigne is extremely elegant and well-dressed. When you get dressed up for a party, you might hope that you'll look soigne.
The adjective soigne is perfect for describing a person who is so polished, clean, and sophisticated that you need a fancy French word to describe them. Soigne comes from the French soigné (or soignée for a woman), from the verb soigner, "to take care of." It's the ideal description for someone who's clearly taken a lot of care to look nice.