Paul, A moisture meter isn't necessary to build wood bows. I bought one years ago and rarely use it. After you get a few bows under your belt and become a little more familiar with the feel and sounds of the wood you will be able to tell if a stave is dry enough to stress or just reduce and wait for it to dry more. Having a good stock pile of bow wood will keep you from being bored waiting for one stave to dry.
We are coming to the dry part of the season so wood drying will happen quicker and stay dryer than in the summer. Pat