All developments or inventions start with an idea, but you must have the willingness to bring it to reality.
Bringing an idea to reality starts with a design. Either a design on paper or with a CAD program.
Once you have a design you can develop a plan to bring it to life. And a 3D printer is a great option for that.
Depending on what you want to do, there are many options
There are a few different printer types. FDM and SLA are the most common, but there is also DLP and SLM which use laser and light to cure material in a very complex, and scientific way.
The number one material use is PLA. It is cheap and effective for printing many items. It also come in a lot of colors and textures.
You can use it as a tool to create objects for prototyping or just for bring a design to life. It helps to hold your design in your hand sometimes!
Use 3D printing for fun by printing an Iron Man mask or an airless basketball. These types of projects are fun and exciting!