I may give you advice that some disagree with, nothing wrong at all with starting with a good Osage stave, in fact I believe it to be your best choice as a beginner. It is the most tolerant of poor(ish) tiller and most any other type of mistake. It will tolerate some dings and violations on the back. The reason I believe some will say avoid it for your first bow, is either an unfamiliarity with it or the belief that you will screw it up anyway so screw up a cheaper board first. Some merit in that, I however say use the best material early on you have available to you. If that is Osage, then you've started with the best odds of getting a finished shootable bow at the end of your efforts. Many on here will walk you thru it what ever you decide. Good luck with it.