Hi Esme, The base of greens and bananas generally remains the same, however, this can be mixed up from a mixture of kale and spinach, to all one or the other. It's also worth considering different types of greens, including lettuce, Swiss chard, beet greens etc
The rest can vary as much as you would like it to, and that includes any supplements for example spirulina, Macao powder etc.
Keep in mind though, the taste will change quite dramatically depending on what you add in or take out.