If you intend to use the leggings for working out, then choose stretchy fabric made using performance fibers/synthetics, such as polyester and nylon. These types of soft fabric are usually opaque, have high durability, and stretch better than other types of fabric. These features are what make them ideal for working out. On the other hand, if you are sewing leggings to wear when relaxing in the house, then you would do well to go for Cotton/Lycra or wool jersey standard fabric. Wool fabric displays better recovery than cotton fabric.