To brainstorm for making an outline, you can use word associations with a chosen topic. Write as many associations as you can.
Example: Benefits of Meditation
Learning how not to react
More meaning to life
See through the illusions of life
Then you can take a certain word or phrase and expand it with its own associations. If you want, you can do this for your favored associations you wrote down, or you can do this for every association you made before.
Example: Inner Balance
Not going to extremes
No destructive behavior
This way, you can have a lot of material for your outline. The next step would be to organize these associations in a favorable sequence so readers can follow your logic.