If I were to design clothes for a fashion show, what would my mindset have to be?

Ok so like say on Project Runway at the end they have the show where they do 10 different pieces... Would the mindset be 10 different themes (like sundress, outdoor-wear, business attire, etc) or would it be 10 pieces that have the same similar theme just different cuts? Help?

If it's the former, can you help me come up with 10 categories?