While fighting the Peggies, you can create many useful items via crafting, such as explosives and homeopathics. There are several missions that reduce the required number of components for craftable items.
When you’re exploring the civilized areas of the world, you will find crafting components such as fasteners, blasting caps, casings, and nitro. These allow you to create explosive devices, such as remote and proximity explosives, dynamite, and Molotovs. These explosives are extremely useful when preparing ambushes or destroying heavily armed vehicles. These are fast to craft and can be cobbled together on the fly while engaged with enemies. However, it’s a good idea to be stocked up before you start an encounter. In order to craft, make sure the item you wish to craft is highlighted in the Weapon Wheel and hold down the indicated button to quickly create one of the desired items.
When you are out in the wilderness, you can forage many of the ingredients for homeopathics. The exception to this is Bliss Oil, which is found on defeated cultists or Angels and sometimes in loot stashes. Homeopathics greatly improve your physical combat prowess. To see the required ingredients for these concoctions, see the Arsenal section in the Appendices.