There are a lot of great sources of information online. I learned a lot about stock investing and trading online (the basics at least). You don't need tons of knowledge if you would just invest. Knowing how the stock market works and what companies to invest in is more than good enough, time is your greatest ally on this one.
However, when it comes to trading, I think that we really need to learn from experience, be it our own or from others. We also need the help of experienced traders especially when it comes to market analysis. Trial and error might do but it isn't practical, you'll lose a lot of money by experimenting.
Never engage in trading not unless you you're equipped.