What everybody else said. I broke a couple when I started, and made a few with chrysals and 3" of string follow. Much of my problem was trying to make bows from green wood. One suggestion I have-go to an event like the TN Classic where there are a hundred experienced bowyers sitting around who wil give you some hands-on advice. I would have started making good bows much sooner if I had done this-it's like being able to walk into the Bowyer's Bible.
Like somebody said, my first attempts many years ago were after reading Laubin's book. Laubin knew his stuff, but he was talking about 48" sinewed osage recurves and stuff that it took him a lifetime of bowbuilding to work up to. I agree with everybody else-get you a couple staves of hickory, white ash, or elm and make a couple of long flatbows to get yourself headed down the right path. And you may find yourself preferring them to the fancier bows you'll build later.