My standard is one outfit per category but depending on the situation I may make them another outfit to wear. In my current save my couple owns a shop so I have added a work attire to their everyday. When they went on their honey moon to Selvadorada I set up an outdoorsy outfit for their everyday and hot weather both the same set, spooky day I made them costumes in their party attire and for their wedding I added a set to their formal.
I also delete sets once their purpose has been served so I won't have to deal with them accidentally changing into them.