It might be obvious, but it all depends on how many people will need to be fed and if you have guests often.
Four to eight place settings is a standard for a couple days' use. If you are looking to entertain more people, you might have to choose between 12 and 16 place settings.
Retail and specialty stores sell flatware by the place setting, but you might be tempted to choose open stock, which sells individually packaged utensils. However, market research has shown that by purchasing an arranged place setting, you can save up to 30%.