Waterston name could have changed over the years from Waterson. If so your family name is a Sept of the Clan Sinclair. If you are not sure about what tartan to wear then use the place of birth i.e. the District of Dundee Tartan. You could if you wanted use your mother's name or your grandmother's name if they had a recognised tartan. The bottom line is you can wear any tartan you can purchase.