The ability to rapidly develop in Drupal starts with a strong knowledge of the ~14k contributed modules. I highly recommend attending a local users group to learn the contributed modules. Short of that, I will help you up the learning curve into Drupal architecture by cherry picking some key modules you can't build with out. This will be a rapid fire talk with one minute spent on each module. Everyone will leave with a list of key modules to investigate.
What questions will your session answer?:
What contributed modules should I start with?
What contributed modules can I not do with out?