I seem to be seeing a lot of new tiers concerned because they don't have the right material to tie a given pattern. Remember that that pattern was developed by someone using the materials they had at hand. The start of every fly is a vision in the tiers mind of some sort of fish food or lure. If this is a natural insect or minnow etc. begin by observing the real thing if you can or research it on the web if you can't. Find a picture on the web. This alone puts you miles ahead of where I started tying. Read about the way it lives and acts when it is available to the fish. Then look at the standard patterns for the thing you want to imitate. If you find one that you have the materials to tie and that seems to match your research your all set. If not then look at the materials you have and think in terms of creating an impressionistic image of your target fish bait. You will be influenced by the patterns you've seen of course. There is little or nothing that is totally new in fly tying. Think in terms of floating/ sinking, smooth/rough and buggy, bulky/ slender and delicate etc. Think of how you need to present the fly and apply the techniques you have learned as well as any you come up with to make a fly. Maybe we'll be reading about your fly next.