So, one of the core elements in the game is Challenges. There are different categories (Horseman Challenges, Herbalist Challenges, etc.) and completing all 10 challenges in a category gives you cash and experience towards one of your core stats (Health, Stamina, and Dead Eye). The challenges are tiered, so you have to complete the Herbalist 6 challenge ("Pick 15 different species of herb") before any of your progress on Herbalist 7 challenge ("Craft and use five Special Miracle Tonics") starts.
One of the problems you have is inventory management. Your initial satchel only stores 5 of each item (or 10 for items like herbs). Some of formulas require multiple herbs (Special Miracle Tonic uses 6 Blackcurrant or Golden Currant, 6 Yarrow, and 6 Burdock Root to make one tonic). If you are limited to your starting inventory slots, it takes a very long time to craft these things. You can upgrade your satchel, first to double capacity for various things and finally to hold 99 of each item. It takes a bunch of perfect-quality pelts to do the satchel upgrades, but the quality of life enhancement is palpable.
A lot of my time has been spent accumulating things so that as soon as I unlock the ability to do a thing, I have the ingredients I need to actualize it. It's much smoother than my first playthrough. It's also less immersion-breaking if I just assume my Arthur Morgan is a packrat who keeps everything he comes across that's not nailed down.