There are 2 waistband styles that are fairly easy to make for a skirt.  The first is a gathered band:  Cut a strip from a sturdier tie (piecing if you have to) that is as long as the top of the skirt is around and about 3" wide.  Fold in half lengthwise, raw edges and wrong sides together.  Open and sew the ends together to make a band, leaving an opening from the about 1" long from the fold.  Sew to the top of the skirt with a 3/8" seam and finish the raw edges with an appropriate stitch.  Cut a piece of 1" wide elastic 1" longer than your waist and insert into the band.  Overlap the ends 1" and stitch.  Close the opening.  Another style next time...