What is it in you that brings you to a spiritual teacher in the first place? It's not the spirit in you since that is already enlightened and has no need to seek. No it is the ego in you that brings you to a teacher.
I absolutely believe in the power of tithing and giving back. My own experience about all the blessings I've had in my life is that the more I give away the more that comes back. That is the way life works and that is the way energy works.