First, where are you located?

There are many ways to get seed. I prefer the wild variety, it tends to have a more hardy propagation system. The flower also tends to produce more beneficial components. I would say, first they need to be stratified before you attempt to grow.

Harvesting, I have found to be best at the peak of the flowering period which is in mid-summer. I use all parts of the plant including the root. I make tea with it. I have not yet done a tincture or oil.

Remember that the YCF is not the Black-Eyed-Susan. It is a cone flower. The Black-Eyed-Susan is a relative, but not on the level of the YCF. When I am unsure of the variety of a specific plant, I first verify, through at minimum four sources, at least one in person. Though the Black-Eyed-Susan is not a toxic plant, I would consider it a waste of time if I were looking for echinacea.

I take the plant while in full bloom, hang dry it and when it is done, crush it and add to my supply. I store my dried herbs in Mason jars. Hope that helped you!