Check out the wealth of information that is on the Internet for the scale and railroad that you plan to model. Learn from what other people have done, but do not be intimidated by it. A small working layout is orders of magnitude better than a huge layout in your head that never gets built. Do not ignore your family or loved ones. Sometimes model railroaders get so involved in the hobby that they loose track of reality.
Skills have to be learned and nobody does it perfectly the first time.
A good percentage of costly things on your first layout can be re-used on your next layout if you so desire. Nothing is cast in concrete. Parts of layouts can be re-done, removed, or enhanced as time goes on. Remember that it is a hobby and suppose to be fun and that you don't have to please anyone but yourself. Photographing a model railroad is an interesting subject in itself.