Originally Posted by InkyMatt
I think it's important to take a certified course, as well as get a lot of experience.
For myself, i know i'm new. I started sailing 8 months ago. I took my Basic Keelboating Standard, read 'The Sailing Bible', 'Sailing For Dummies', and 'The Complete Sailor'. After that, I logged over 150 hours this summer cruising and racing my club's fleet of J24s. After one season, i'm quite capable of safely single-handing a small keelboat. I also know that I'm not familiar enough for the 30'-plus yachts yet. That's what I'm expecting my Intermediate Standard to help with.
The summer's cruising/racing experience taught me much more than the course did, but the course went through the safety aspects that are necessary and often overlooked if you just buy a boat and cast off. Similar to taking Drivers Education before getting your driver's license, you'll be fine 99% of the time but might need that special training for the dangerous 1%. To me, the danger of not knowing what to do in an emergency justifies taking formal training.
You have expressed very well the need for both experience and training. I often tell prospective instructors that they need to have made a lot of mistakes before they can teach. There is nothing quite like saying "and when that happened to me ..."
You can also use the experience of the instructor to avoid some emergencies.
In many ways dinghies will help to improve your sailing skills, they will not be of much assistance in developing cruising skills and knowledge.