Ok I've narrowed my choice down for the new outfit to the side button skirt and the flare skirt.
Her panties are probably going to be the see thru one. So I made a screenshot of few combinations.
From the panties I like the black and pinkish the most.But I also like a bit of contrast so I don't think combining a black skirt with a pair of black panties is the best choice. I've added it to the example anyway.
They actually come in white as well but somehow the white are a lot less transparent and don't look as good as the others.
I also included an example using a darker denim skirt with black panties to create a bit of more contrast , but I think the lighter denim skirt will work just as well.