Try a board stave, they make learning easier- no knots, humps, dips, etc. But mulberry will make a GOOD bow. Its a cousin of Osage, which is an amazing bow wood. Choose a piece of hardwood(hickory, ash, red oak) with parallel rings on the back(a series of parallel lines running down the back). It will help you learn tillering without ruining expensive and hard to get tree staves.
Black locust teaches you to tiller, pretty much any hardwood makes a good flatbow- ash, elm, hickory, black locust, honey locust, oak, hard maple... the list goes on. I just started making hunting-weight bows a few years ago... Red oak 1x2 makes a nice good longbow. I don't live too far from you, find your nearest Home Depot and get a 70" red oak 1x2. Then leave the central 12" full width, then narrow to 1 1/4 9 inches from tip, then narrow to 1/2"tips. thin as neccessary to get correct tiller. That makes a nice, fast, low-set longbow. Also- with red oak, you want to keep the belly as flat as possible.