One of the best books on marketing that I have ever read is Brian Tracy's book, Marketing. Perhaps it's because of the basics he talks about, or maybe it's easier than that. The basics are all you need, so with this book you have one of the clearest paths forward. Marketing is your long-term growth plan, which is more than the short-term sale. One of his other books, Advanced Selling Strategies is also a book that is essential for anyone who wants to convince someone to buy their product or services.
Buy these two books, do your homework, implement the strategies and your company is going to be in a lot better shape than most of the mom and pop shops I know of. It will be an impactful $25-$30 well spent that could potentially change your life.
Your company is an extension of you; the stronger you are, the stronger your message is, the stronger your company is. Don't wait! These books are an amazing investment into yourself. Every music teacher hoping to be teaching professionally in a competitive environment should read them before they leave college. Thinking of opening a music school? This is required reading.