Proper ensemble or self expression in clothing

Which is more important? I’m speaking in terms of toddlers-elementary school age as they gain autonomy. For example if you child wanted to wear a dress and a tutu with winter boots. Or if your son wanted to wear his sisters dress to school. If your child wanted to wear different shoes on each foot. I’m not just referring to one time but everyday. Just curious what the boundaries are between self expression and learning how to dress according to “conventional” standards. I don’t have any particular position on this issue but genuinely curious as to what others think.