chiffon- (nylon) a sheer, soft, limp fabric. Chiffon is elegant & "flowing" with little body/stiffness. Because chiffon is soft with little body/stiffness, it typically requires more yardage to provide fullness in a petticoat. A popular choice.
organza- (nylon) a sheer soft fabric, like chiffon with more stiffness/body. Organza is a comfortable elegant with more body/stiffness. Organza petticoats tend to be fuller with less yardage, therefore a little more light weight.
Net- (nylon) a more sheer fabric with LOTS of body/stiffness. Net is generally used for the top/outer or middle layer(s) of a petticoat to provide maximum fullness while the under layer (next to the body) is generally organza or chiffon for comfort. Net provides the maximum amount of fullness with the least amount of yardage and weight.
crystal- a sheer soft fabric with the extra body/stiffness of organza while also having the softness of chiffon. Crystal has a beautiful "sheen" or subtle sparkle making it very elegant & "high end" and providing a stunning more dressy look.
Hemlines- Fluff (ruffles) or leader line on the hemline will add fullness to the bottom of a petticoat while a simple hem or lace on the hemline will be a more relaxed fullness.