The best way to get herbs for your magickal spells and rituals is to plant and grow them yourself. That way, you know where they have come from, the nutrients they have been given, and what they feel like to live with. -- In other words, you know they won't have absorbed the bad energy associated with exploited workers, or have a huge carbon footprint, having been flown thousands of miles from distant countries. You can avoid the use of chemicals on your herbs which is important, as you may need to eat them as part of a ritual. Also, you can add your own energies as you tend them while they grow. After all, magick is all about getting the energies right and influencing the universe in a positive way.