Beginner tips come in snippets on this website, so I spend much of my alone "down" time in the evenings reading posts. It's quite helpful, but it's a huge, general website with advice on EVERYTHING. As for the "start here," I wanted to make a small cake for my daughter's birthday, so I googled buttercream recipes and came upon this website. Instant addiction and now I sell my cakes locally.
The best way to start is to bake cake, frost it, decorate it and figure out what you want to do better and what you want to learn the most. Then, search this website for how to improve. Was the recipe lousy...search recipes. Was the fondant crumbly? Search fondant. Was the whole thing a disaster? Take a picture, post it, and ask for input. It's all trial and error and it all depends on what you need the most help with.
Have fun and enjoy the forums!