Things you are going to need to complete the Instructable and Launch your own 3D Printed Rocket are put together in a comprehensive list in an Excel Spreadsheet with links to the components I used - You can always use your own if they are laying around!
For the actual rockets - I highly recommend designing your own or finding one on Thingiverse.com. Also having a 3D printer, experience with Arduino, and knowing how to solder will be incredibly useful in making the launcher and launching your own 3D printed Rockets!
Also if you are under 18, please acquire an adult for supervision! You will be using (controlled) explosives later on!