So, is there a way to permanently increase the Experience you gain when doing actions in Forager that award Experience? Yes, there are a few different sources actually!
We will go into detail about the different method, but one thing to keep in mind is that they stack. This means that you should work on getting multiple things to increase your Experience gained permanently, since they will have a additively effect!
#1) Craft books at the Inscription TableWhen you unlock the Inscription Table, you will be able to craft books. The first book is called "Moldy Book", and it's considered a non-usable tool, which means that you can craft it once, and get the bonus from it from that point on without having to do anything. The Moldy Book will give you +15% bonus Experience whenever you do anything that yields Experience. You craft it at the Inscription Table for 4x Thread and 4x Paper.
Once you have the Moldy Book, upgrade it as much as possible. The next upgrade is Slimy Tome for +30 % Experience (4x Leather, 4x Paper, and 4x Jelly), followed by Necronomicon for +45 % extra Experience (5x Royal Clothing, 4x Paper, and 4x Bone), Glacial Scriptures for +60 % Experience (5x Fiberglass, 20x Paper, and 40x Crystal), and finally the Hellfire Glyphs for + 75 % Experience (4x Fiberglass, 4x Paper, 4x Demon Horn).
The books do not stack, and only the best one is active, so when it's fully upgraded you get a total of 75 % bonus Experience anytime you get Experience points in the first place.