I found a huge bag of buttons very cheaply in one of the bargain bins at a craft store. I sorted through them and found some pretty blues, greens, grey, white and clear ones that looked nice together. I strung them all on a string - does not seem to matter if some have four holes and some have two... here is my very simple button necklace.
Not the best photo - but you'd be surprised how difficult it is to take a picture of yourself in the mirror with one hand and keep your shirt and the necklace looking OK!!