I made a very simple button necklace recently. Just using bead thread and old buttons, the only other requirements were a safety pin and a needle. The buttons I used are nothing special. I think they were bought a few years ago as a bag of red, green, yellow and blue plain buttons. If you have special buttons that are just sitting in a tin, use them. Maybe you've inherited some buttons from your mother or grandmother. They would make up a very special necklace and have the added bonus of being useful again.
Start by deciding your colour or size pattern. If you want to make one like mine, just tip out the buttons and start threading. You'll need some bead thread, cut to the size of your finished necklace. Thread it onto an ordinary sewing needle with the other end tied to a safety pin, so the buttons don't slip off the thread.
If you're only doing one colour, sort them out first. If you want differing sizes or a set sequence of colours, work out your pattern on a flat surface first, then thread the buttons one at a time from the laid out pattern.
Thread through two holes only, even if there are four holes. The buttons will tend to fall in a certain way, let them do that and push them as tightly as possible up against the preceeding button. Push all the buttons you've threaded right to the end of the thread near the safety pin, allowing for some thread to either make a knot or to add a clasp. It's too difficult to move them along later then there are a lot of buttons on the thread.
When you have enough buttons on the thread to make the length you want, go along the thread and push the buttons together again to tighten the line. When they're all tucked up nicely, you can tie them off - which is what I did, or you can add a clasp. You'll need a clasp if you're making either a bracelet or a short necklace that won't fit over your head. If you're a sewer, you may have a hook and eye, similar to this. That will work perfectly. Otherwise, buy a small clasp from Spotlight or your local craft store.
And here is the finished product. Please disregard the model who looks like a deer caught in the headlights. She is the only one I can afford. : - )