I start them with 5 outfits in Everyday, Hot Weather and Cold Weather (the other categories tend to get a single outfit) but I do change them up when we get new content. or when they age up to Adult from YA and I feel they should have a more mature look. In my current save I'm working to have my family unlock all the career outfits so I'll have access to everything when dressing my Sims in that household. (Haven't decided if that includes the GTW careers.)