In the past I have ordered from both Kalyx & Z Natural (although not ashwagandha). I was satisfied with the service & the herbal quality.
Ashwagandha is a good starting point - you want to start with one tablespoon daily (I take it all at once, but some prefer to split it up into 2-3 doses). I've also taken twice that much with nothing but good effects.
As natural as it is, and as fantastic as a 'symptom reliever' that it can be for some, remember this is not a cure. It's simply a way to get some good balance & symptom relief so you can get started on the real healing process.