There are a number of ways that you can contribute to help make Octave a better system. Perhaps the most important way to contribute is to write high-quality code for solving new problems, and to make your code freely available for others to use. See https://www.octave.org/get-involved.html for detailed information.
If you find Octave useful, consider providing additional funding to continue its development. Even a modest amount of additional funding could make a significant difference in the amount of time that is available for development and support.
Donations supporting Octave development may be made on the web at https://www.octave.org/donate.
If you cannot provide funding or contribute code, you can still help make Octave better and more reliable by reporting any bugs you find and by offering suggestions for ways to improve Octave. See Known Causes of Trouble, for tips on how to write useful bug reports.