Speaking where I have no business speaking, if you are trying to get a handle on lighting, I would shoot in JPEG at first. I look at it as being like the difference between shooting slides and negatives. If you wanted to learn about light control back in the film days, you should have shot slides in my opinion. That is because there was no one between you and the finished product, including yourself. Nothing was open to interpretation. What you saw on the slide was what you got when you exposed it. With a negative, the printing phase allowed for all kinds of adjustment and misadjustment. You may or may not have gotten what you were after depending on how it was printed. Even printing my own color negatives, I fiddled with them and subjected them to interpretation. I could create what I had in mind, but the negatives were too forgiving for me to have learned much from. A similar situation exists with raw and JPEG. Raw, like a negative, is designed to be fiddled with and is very forgiving. The end result may be much better than the same image shot in JPEG, but adjustment is required to get there. So practice with some JPEGs. When you get so you don't blow the highlights or send the shadows into oblivion when you didn't mean to, then you have the basis to start playing with raw images. Just my two cents worth.
