I sometimes "prescribe" potions. I have two ways to prepare them.
One is making teas and infusion with herbs that have a active principle known to be helpful for some issues, so Fennel, carvi, licorice and anise for stomach and fermentation. I always use a special prayer on the herbs to invoke and thanks Mother Nature for the healing power the herbs have. This kind of potion can't be strictly said as magic, it is more being thankful to the Nature for the chance to use herbal remedies. Sometimes I use techniques that belongs to Spagyria to prepare powerful remedies, but it takes a lot of effort and time.
The real magic potions that I have prepared in the past have nothing in common with teas and not always are meant to be drunk. I usually do not give a potion in order to satisfy the request of the person - e.g. Someone asks a potion because he/she needs more energy. I first look at the subtle cause of the issue and I cure that one with the potion - e.g. you feel not plenty of energy because you spend it at work, everyday, in order to be cool and show off in response of a serious lack of confidence or you never remember your dreams because you avoid to confront with your colleagues on a hot topic, so when you do it in your ... and so on.
you take ingredients that have a metaphysical meaning and transfer their properties in a medium that acts as vehicle, like water or wine for example, by means of prayers, invocations to spirits that govern elements and aspects you want to transfer. So basically you have to find the ingredients that possess the particular property that you lack or want to balance in your life and act the transfer.
I guess anyone can find the right potion he/she needs invoke your guardian spirit and ask to be guided in the choice of the right ingredients.