This pattern uses foundation single crochet stitch and the magic circle technique.
Fsc tutorial: http://www.crochetspot.com/how-to-crochet-foundation-single-crochet-fsc/
Magic circle tutorial: http://www.craftsy.com/blog/2013/09/demystifying-the-magic-ring/
Gauge is unimportant for this pattern.
You will need yarn for the body of the frog and for the whites of the eyes. I use black yarn for the pupils, but safety eyes can be used instead.
One skein makes multiple frogs. They can be made with scrap yarn.