Speaking for myself, I think it is good to begin by working with a style that you feel confident in, improving on your strengths, and then once you've mastered that style (or have become bored with it, whichever comes first), move on to something new. It's good to try a range of different things though, and some people move from style to style with amazing swiftness. I guess it depends on what you are comfortable with and what motivates you. When I first began here I knew nothing about cartography or digital art. Ascension's Atlas tutorial (translated by Gidde into GIMP) was a huge confidence builder for me, since it enabled me to make a nice map without much in the way of background knowledge. Over the years I've worked on refining my own method similar to Ascension's. I always had the intention of moving onto other styles once I felt I had mastered this one. However I've found that I have little time for mapping these days, and since I've mostly just worked in this style when I'm asked to do commissions it is this particular style that I am asked to work with, meaning I haven't been able to do branch out as much as I'd like. So that may be one reason in favor of trying out different styles from the very get-go. Don't know if that was at all helpful or not.