The short answer is probably one. The long answer is that no one really needs any spices at all. Sure, they add color and taste to your food, Incense powder but they can easily be replaced with hot sauce or salt & pepper. However, if you consider that spices have been used for thousands of years, have a function (to preserve food) and are a huge part of culture, then you might want to look at spices in a new light. But if you're still looking for a very short answer, just get one or two.