There is no minimum or maximum number of arguments that you should have in a debate. The number depends on a great variety of factors. When a debate is long and much expected (such as a debate between political candidates), the number of arguments can be very large. In smaller debates, due to the limited time you have available, it is difficult to address more than 3-5 arguments. However, as a general guideline, 3 might be a good minimum standard to set for non-professional debates.