17th century buttons were not pierced with two or four holes like those found now. Instead they had a shank on the back of the button, and the single attachment hole passed through that. This image courtesy of the Portable Antiquities Scheme.
Metal buttons were common, often made from lead, pewter tin or alloys of the same. These were usually cast, and the shank could be formed as one piece with the button, or could be in the form of a twist of copper alloy or iron wire set into the casting. Metal buttons could also be made from copper alloy, either cast as above, or in the case of flat buttons, punched from sheet with a loop soldered on the back. Buttons could also be made from wood, bone etc, but these styles were also shanked not pierced. Upper class buttons could be in silver, gold, or precious stones.
Another style of buttons used a core, often of wood, covered in a wrapping of threads. The threads also formed an attachment shank. They could be fairly plain and simple, or use expensive silk or silver and gold thread.
Things to avoid:
These are clearly not correct: plenty of authentic buttons are available and are frequently cheaper than buying modern buttons.
They were not used as buttons in our period, although they could form the core of thread buttons or cloth buttons.
Period buttons always seem to have some form of shank.
Wooden or other buttons which are very shiny, non native woods etc.
Wooden buttons would probably be small scale rural production. As such they would not be highly finished or use exotic woods. Ordinary grade metal buttons would not have a modern machine polished high gloss finish.