from experience, if you're not going to use a stretch fabric, DO NOT make the collar one piece with the rest of the outfit. It just never works. believe me, i've tried. your best bet is to make the collar separately.
for the shirt i'd use this pattern: http://www.simplicity.com/p-5826-mis...-or-shirt.aspx
and alter the bottom so it's not just flat but more rounded. just don't make the buttons
the skirt is actually really easy to edit from any skirt pattern without pleats, just add a slit to the left side