Allison on why there is relatively little help available for people self-teaching probability

I believe there are several reasons why there is so little help for discrete probability at this [beginning] level:

1. It requires significant mathematical maturity to even begin to understand what's going on.

2. Almost no one understands probability anyway.

3. Even if you do understand, it is extremely difficult to be careful and precise enough to never make a mistake in describing the problems or wording the solutions.

4. Most of work in discrete probability rewards cleverness. Few methods for tutoring individuals, or supporting individuals in their own learning can teach cleverness.

I'll elaborate on these in another comment.

But this is where you should start: Schaum's Outline of Theory and Problems of Probability (2nd edition)