Here is a Baby Bonnet made in 3 pieces with finishing off with a Scallop Brim for the girls and Normal Brim using Short and Reverse Short Rows on the front of the work. Then add some Intelegent Cords for ties or sew in some ribbon.
I used what I had in my stash but guessing that no more than 2 skeins of baby or sport 3 ply yarn is needed.