It sounds like you already have a good base to stand on and aren't literally starting from square one. Start researching network/website security and see what interests you. A lot of us here have a particular specialty because that is what interests us. You've already got a good start on the challenges too, so that is good.
What would you like to learn? What do you know about that you have been meaning to learn more about? Your question is really specific for every person. I can tell you a whole lot about hacking wireless networks but you might be really interested in programming viruses. See what I mean?
"The quieter you become, the more you are able to hear..."
"Drink all the booze, hack all the things."