Ask your customers what they need. Be realistic: if you happen to live in a very warm country, you will have a tough time selling ski jackets. Look around you. What do real people need and want. For example, if you plan on designing a complete collection, you will need more tops that bottoms because most people have more tops than bottoms in their wardrobe in general. Tops are great to change your looks while a plain nice fitting pant will match most of your tops. Keep it simple and realistic. Extravagant sketches are nice on paper, but great tops and jeans will sell out in more interesting numbers than evening dresse.