You can look at studies done using psylocybin for a start, but also, adjust based on your own experience. Most people use between one and two grams of mushrooms, with two grams being quite strong strong for many people.

Some people are tempted to push the dosage so far as they can take it to experience "ego death", and I don't think that's necessary for therapeutic effects. Not quite sure how safe it is to push the dosage as high as you can either. There's some kind of esoteric belief in some circles that you'll get some magic enlightenment, connecting with another realm if you trip hard enough, but imo that mostly attracts people who already have fragile mental health.