We use fresh oregano because we grow it in the garden. The leaves from one long sprig is about a tablespoon. Dried oregano is fine but you'll have to reduce the amount to make sure that the aroma and flavor or the herb does not overpower the soup. Half a teaspoon will do.How much salt you need to add depends on how salty the vegetable stock is. If it's unseasoned, you'll likely need a teaspoon and a half.