Looking at leaning more about potions. Im big into herbs and being an herbalist (but I also believe in medicine), and have always been curious about and interested in the properties of herbs that we have forgotten.
Trai, there is a lot which isn't necessarily forgotten, but much has fallen out of common use.
One of the most recommended books I've seen is Cunningham's Encyclopedia of Magical Herbs. But there are also a lot of plain old nature guides, which cover a ton of medicinal and edible uses. These, in my opinion, can be good because you can find them specific to your own region. Of course, it would be recommended to have not just a basic guide for the region where you live, but also a more in-depth guide or two, to find alternative uses, and more ways to use and process the plants local to you.
Also, welcome to SoM! You've found a good community.