2) They should be bronze or brass, look for "A Grade Zills"
3) They come in difference sizes, a good size for beginners is 2" in diameter
4) I recommend the ones with 2 slots side by side (instead of one single hole) This is for the elastic that will go around your finger.
5) Some come with elastic, some don't it's okay, You can purchase a small piece of elastic from your local crafts store.
Another high quality option that I would also recommend