The
key to being a guru is to develop a few
memorable counter-intuitive statements,
e.g., "Avoiding
risk is the
biggest gamble of all."
If you have those, a touch of charisma, and reasonable skill with the Socratic method, you don't need any real expertise to build a reputation as a guru. Add a laptop with a portable projector, a laser pointer, and some skill with PowerPoint, and you can make a living as a professional guru.
When you achieve Tony Robbins-stature, you can get by on more cryptic statements, such as "Feel my skills, donkey donkey donkey, donkey donkey", or "Do or do not, there is no try".