This is cannabis, I don't think you ever actually get "prescribed" your medically necessary recreational activity.
but in California, for example, I could simply just ask the doctor writing my cannabis prescription what's their dosage suggestion based upon the medical reasons they were writing my presciption in the first place.
But you're not wrong. If you wanna figure out what works for you, you'll have to experiment for yourself without a medical professionals help. That's true for any over the counter (OTC) medication in your local pharmacy, too.
The best guess I could give you for a "minimum therapeutic dose" for THC/CBD would be 5MG. Start from there and move your way up to what works for you.