All three woods can make a good bow. As Mike explained, you need to match the design to the wood species. Easier said than done though, especially for a beginner.
Will you be using a board or a split stave?
Myself, I'd go for the ash. It's easy to work with and usually straight grained. Next on my list ywould be the maple, but not the European species of maple. A maple board is usually an American species, which is stronger than the European equivalent. Oak can be greatly variable in quality, especially European oak, which is also not often straight grained.