There are just a few outfits that can be used normally (in the hotel) since depending of the outfit might have an interaction with the girls when you encounter them outside of their rooms, for the most part most of the outfits can either be used during their repeatable scenes and only there, still there are a few like kali's bunny suit that are needed for the game to progress so its a good idea to buy most of them, to use them in the hotel for the most part are at least 3, the normal outfit (default), their slutty outfit and the ropes, the slutty can be bought but the ropes well in that you will need to know what to do to unlock it, there are some girls that have more outfit available to use in the hotel but not every outfit is usable like this.