The poncho is one size. For the basic poncho, without border, 4 skeins yarn are enough. Depending if you want to make a border and how wide you want to make the border, you will need an extra skein of yarn.
Because of the big hooksize the poncho is quick finished.
The stitch used for the poncho is a variation of the moss-stitch, with half double crochet instead of single crochet. The border is made with front and back post double crochet.
With the yarn left you can make a matching hat, the pattern is included.