There are many spells involving herbs in them. Like protection.
Like a protection spell without the herbs, you have to have intention for the herbs to work. You have to focus on them.
There are also powders in such that have magickal properties, like prosperity. You have to have that intention and belief that it will work. If not, they would be just a powder of herbs, nothing more. It's the energy, belief, and intention you put forth that will make a spell work.