DAD seems to be the most common/preferred tuning these days. DAA (low to high) seemed more prevalent a couple decades back. Do you have access to a good repair/set up person who can check your intonation? When I first got a dulcimer kit in the early 1970's people were tuning to C rather than D. I think the change upwards was to be able to do more fiddle tunes with other instruments. When I started, I primarily used a popsical stick as a noter on the melody string. I later just used a finger and then could do occasional chords. My wife doesn't play melody at all and just uses chords, so there are many ways to play a dulcimer. I hope this information is useful. I'm sure there are others with more practical set up experience that may comment.