Most items, potions, and ammo in GreedFall fall in the category of consumables. You can purchase them from a merchant or vendor in the game, or you can craft them yourself if you have the correct ability.
GreedFall – How To Craft Items, Potions, And Ammo
Crafting items, potions, and ammo in GreedFall require the Science Talent. There are three tiers of consumables, and each talent level in Science that you purchase gives you access to a new tier of potions.
There is another advantage of the Science talent, as it will also allow you to use explosives to break through weak parts of walls, which can be very advantageous in some areas and missions.
For people who wish to use Firearms, Science is a vital talent so you can create your ammo. But you need to get to Science level two to do this. At science level one, you can make health potions, which are essential no matter what variety of character you are playing.
To craft consumables, you need to find a Workbench. You can find these in towns, and you always have one at any camp you set up or your residences in the various cities. Just head for the workbench and interact with it, then navigate to the consumables tab. Scroll down to the item you wish to craft and make sure you have the required science level and ingredients. If you do, you can craft the particular item.
To ensure you always have plenty of resources for crafting, be sure to interact with any glowing items that you see in the world. You can find resources in trees, crates, various bushes, chests, and on the corpses of monsters and creatures that you kill.