My help will not be what you want to hear. The best statement you can possibly do is one that comes from you and you alone. One that sets out your philosophy and beliefs about teaching and learning. One that says who you are and what you will bring to the profession. No-one else can possibly do that for you. And, to be frank, (which is not always a good thing I know!) if you cannot manage a statement as to why you should become a teacher, you probably don't merit a place on the course.