Sewing and fitting clothing are very different from blankets and quilts. I would look for something that is semi-relaxed or relaxed in fit. I would look for a tunic, or maybe a a tunic that could be extended to dress length. You may need to do a full bust adjustment.
Underlined linen (underlining makes linen wrinkle less) and underlined cotton would be good choices. You might also have to add a lining.
I like the simple dresses in this book, but have never sewn them. You may also want to explore Japanese pattern books, although some American women find the size range too narrow.
Sewing Patterns Review is another place to post this query.