Promotion

I’m thinking of starting a small dance troop once we start getting paid, how much of that money should I spend on promotion, and as I get bigger does the percent grow or shrink?

My potential business partner asks me to write a business plan. In the business plan, I am required to write how much money is required and what effect that each investment will bring about respectively. But I feel it is difficult to predict exactly what effect that each investment will bring about respectively, especially web site promotion. How can you predict it, especially you are facing a new field that almost no one has done it before?