Group A is guarded by a learning curve like the Swiss Alps. The only way to get past that is to get as much exposure as possible. There are already some excellent suggestions here so I won't rehash those, some other things you might consider:

Idle in #drupal and #drupal-support. Whenever an interesting question gets asked, go figure it out if you don't know the answer already.

Try tackling a few issues in the novice queues for D8. Not only will you get the kind of low-level exposure to how core really works that so many "Drupal developers" lack, you'll also get some nice bragging rights when your name's listed with the rest of the contributors.

The next time you encounter a limitation with a module you're using, in addition to hook_$N_alter()'ing the fuck out of it, try writing a patch that cleanly extends the module to do what you want. Open an issue in the module's issue queue and submit your patch. Code review can be tough to take but stick with your issue until your patch is either accepted or the module maintainer closes the issue (won't fix, whatever).

Try landing a gig with Acquia or some other big Drupal shop. You'll get to work with (and learn from) some of the top talent in the community and you'll get the kind of exposure you can't get experimenting in your spare time.

If you're serious about going pro with Drupal development drop me a line. I may be able to help and would be happy to introduce you to others in the community.

I had a lot of difficulty finding good learning resources for developers. Most are aimed at non-programmers. I had quite a few questions answered on http://drupal.stackexchange.com/, which is a good starting point.

- Write a module with at least some UI to scratch an itch. - Then figure out how to contribute it to the community as a release on drupal.org.

Both parts of that process are equally valuable.

Try learning Drupal from a person first. A meetup or a Drupal camp are very good. A video is the fallback: Try NodeOne:

http://nodeone.se/sv/learning-library

or drupalize.me:

http://drupalize.me