K.A.
My daughter wears them with anything and everything. If it's warm she puts a pair of spandex shorts under it, if it's colder she wears leggings or tights and has been known to have a pair of jeans or fleece pants underneath if it's that cold but she still wants to wear one. She wears whatever shirt she wants to. Shoes are the same. So long as it's weather appropriate, anything works.
You can find her wearing her "puffy skirt" as we call them with a Spiderman shirt, bright colored leggings and snow boots when she's so inclined. Other day she's wearing a glittery blouse and a pair of sparkly mary janes.
Have fun with them! That's what they're best for!