Hi MMG - It was nice shooting with you last weekend with the Bandidos.
Good advice above. I'll just add how I ended up with my current recipe. It happened as I was able to get an 8 lb jug of Clays thrown in with the press I purchased. That's what drove my path forward. From there I went to the books, Lyman Shotshell Reloading Handbook, Hogdon online , Alliant online and others to find my starting point. And it's definitely nice to see what folks here are saying to be sure I was on the right track.
So as already been mentioned - see what powder you can get your hands on. Great if you have multiple choices. Go from there