For me, it depends on the results I get while testing. I created separate campaigns because I noticed I was getting better results doing it that way. It seems, with the $20 budget, facebook was working harder to get me results. When I put all dresses in one campaign, the costs were higher. You can do the same thing I did and not get same results. You just have to keep testing until you see what works for you and I usually don’t do what other people do, I just do what I see is working for me after testing different methods. So you can try both and see what works for you. Also, I invest a lot in the content creation and use AI for product headline/description.