You can never have enough method books as a trumpet player. There may be many books about the same things like buzzing, long tones, articulation, lip flexibility, and more. However, each book has it's own unique take on the subjects and offer different ideas for your practice. Money is limited, but when you have the time I suggest you add these books to your collection if you haven't already. I will list some of the books I think are essential to beginning and intermediate students. If you click the images the link will send you to an external webpage where you can purchase the book. A quick tip for music buying, Amazon is always great, it's also faster and great to support local if you have a music store near you. However, if the books are not in stock, look around first. Music publishers have been pretty slow over the past few years, if the book is out of stock it could take months for them to get another in stock.