First thing to remember is that you will probably have little-to-nothing to lose by diving straight in. Worst case you fry a $35 board, but the chances of doing that from your keyboard are tiny. If you somehow knacker your operating system, you should be able to revert the SD storage cart to its original state and start again.
That said, I"d suggest a good way to kick off your learning is by looking around for projects others are working on, and picking something you think would be useful/cool to have. Chances are someone with more experience will be doing something interesting soon after launch, and sharing their code with the world at large. Find something that doesn"t look too ambitious and grab the code. Depending on how clear their instructions are, you should be able to recreate their results, even if you don"t actually understand any of the code at first. Now you"ve got something cool/useful, and full access to the code that made it. Try reading some of it; so long as the author is a half-way decent programmer, you should be able to follow some of what it"s actually doing simply by reading it as though it were a set of instructions written in English—for instance, while some lines might be unobvious, you might see something like "while (something) do (something else)", which does exactly what you"d expect. You may even see something that you could try customising for your own perferences: try it; if it works, great; if not, oh well.
Years ago, in the age of computers like the Spectrum, Commodore 64 etc. there used to be magazines that would have sections where they presented code listings for simple programs that you would sit at your keyboard and type out faithfully, whether you understood how they worked or not. I believe this sort of hands-on experimentation is far more valuable to people with no programming experience than any structured course could hope to be. After all, we all learned to talk simply by being surrounded by people nattering away, rather than being sat down at the age of 2 and told how to decline a verb!