Starting with a white cotton dust ruffle made for a full size bed, I made a new petticoat. It's comfortable, inexpensive, and easy to sew. The dust ruffle itself was $2 at a thrift store and the only other expenses were white thread and a package of elastic (another $2).
Besides the money saved by purchasing a used bed ruffle instead of new fabric, this project also saves a lot of time and energy. Since there is already a ruffle attached to the cloth, there is no need to make one along the bottom of the skirt.
Lay the fabric out flat and cut off the ruffle along the short end ( see the red lines on the diagram). Then cut down the middle, longwise, making two equal parts, each with a ruffle.
Place the two halves together, right sides facing each other and sew up the sides.
Iron over a 1/4 inch fold all the way around, on the side with no ruffle. Using that fold as your new top edge, fold the fabric over 2 inches and iron down.
This will be the casing for the elastic waistband. sew down, leaving a 2 to 3 inch gap to feed the elastic though. Pin a large safety pin to the end of your elastic so that it is easier to grab and pull as you feed it through the casing. When the elastic has been pulled all the way through the casing and come back out the other end, overlap the two ends of the elastic and sew together. Pull the waistband until the elastic is fully inside the casing and sew the gap, through which the elastic entered and exited the casing, shut. It is now ready to wear.