The concepts of "boyish" and "girlish" ways of dressing show how deeply ingrained in your minds is the gender categorization. The way you dress shouldn't be any indication of your gender.
We've come a long way with jeans, t-shirts and sneakers , which are pretty much unisex in most westernized societies. But they still managed to make them "gendered", with the jeans button being on different side for men and women and making different shoes colors for men and women.