I find that when I'm creating a chord progression from the harmonic minor scale that using all of its native chords sound weird. I'm specifically talking about the III augmented chord. Using III as a major chord sounds better, but it would seem that I'm borrowing from the natural minor scale. When I took Classical theory lessons I found that they only used the raised 7th in the V chord and in the vii dim chord. What are the rules for using certain chords in minor scales? There's also the melodic minor scale. Is this used for chord progressions at all?
Here are two flow charts from the Kostka harmony textbook, one minor the other major:
You are right in that the chords come from the natural minor except when the harmony is dominant in which case the raised leading tone is used.
In terms of root progression, the two charts are nearly the same. So, while there aren't actually "rules" the basics of root progression are the same when comparing major and minor keys.
Tonal Harmony by Stefan Kostka, Link: http://a.co/alEKzeD