Much depends on your gameplay and style preferences, of course, but I've found that I use the sparkly formalwear from Luxury Party a lot (it's great for Aliens, entertainers, and rich Sims with questionable taste), I enjoy the movies and popcorn from Movie Hangout and use the decor more than I thought I would, and I love the garden decor and the fountain from Romantic Garden and like that I can use the wishing well to generate a bit of unpredictability when I'm comfortable with that. I have Perfect Patio and Cool Kitchen but use them less in practice.
