Growing new plants can be as simple as cutting a small piece off the original plant and poking it in the ground.
In many cases however more care is required and it helps to take the appropriate age wood at the correct time of the year and then provide the suitable conditions to ensure it grows its own roots.
Details
There are many ways to obtain healthy plants for next to nothing. By propagating your own plants you not only save money but can introduce genetic variation by starting new plants from seed.
If you are looking to replicate a natural ecosystem or create a biodiverse and healthy garden you are going to need a lot of plants. Many species can be cloned by taking cuttings or by layering.