That's sort of like asking what ingredients are needed in most recipes. There are a few magical ingredients which are useful in a very general way, such as sage and dragon's blood, but the vast majority of herbs have specific lore, uses, and dosages, and you will need to study herbalism to learn about them.
As the person above stated, there are different correlationtions in herbs depending on the folklore or path you are studying. Sage and dragons blood are very well used, but I would say sage is the better of the two. Sage is used by most cultures for relatively the same reason, as a purifier and a promoter of general well being of whatever they are trying to promote. But I cannot single an herb out and say it is the best, because all herbs server their purpose and are just as important as the next.
Aside from what has already been stated, herbs are generally associated with the intent you have for your spell or potion. For example, if you are casting a spell for protection then you would use herbs that corresponded to that intent such as sage, bay leaves, garlic, etc. If you were casting a spell for love you would use herbs such as rose, violet, or rosemary and so on and do forth. If you have a favorite herb then I suggest reading up on it's properties to find our which spells or potions it would be best suited to.
Also, if you would like to read up on this topic, I would recommend "Herb Magic for Beginners: Down to Earth Enchantments" -Written by Ellen Dugan.
"Herb Magic for Beginners: Down to Earth Enchantments" -Written by Ellen Dugan.
^As You can see, I use this book fairly often myself.
There are plenty of herbs used for magic works, here are few popular ones i know:
White Sage : A powerful cleansing and purifying agent, white sage is included in all of our amulets. It helps to enhance the powers of the other herbs in the blend. It is very popular for smudging.
Salt : While technically not a herb (it's a mineral), salt is often sold with herbs and is such a useful tool I couldn't leave it off this list. Salt is used for cleansing, purifying and protection. A circle of salt around your sacred space will help block out negative influences. Negative energy can also be cleansed from your tools by allowing them to rest overnight in salt.
Sweetgrass : Like Sage, Sweetgrass is a powerful cleanser and protector. It carries a powerful female energy. We keep a sweetgrass braid over our door to keep positive energy flowing in our home. Sweetgrass is also very popular for smudging.
Basil : Basil is useful for both money drawing and healing.
Cinnamon : Cinnamon is a powerful stimulant in magic. It increases both energy and passion.
I can not say those are the most popular ones, but they came up into my mind when i saw this thread, and as i said there are plenty of herbs.
The magic of herbs - medicinal use of plants for the forces of human health and magic rituals. Be sure to know the grass, feel them, not to be confused with no sense and realize that every plant gives energy and is curative.
In order to obtain the greatest effect on the grass, it is collected in a suitable time for this. You should know that all animate and inanimate in nature can be used as a detriment and the benefit.
The first thing you should pay attention - time of day, phase of the moon. This affects the quality of all growing plants in a given period. For bright magic rituals to gather the best grass at dawn, to the growing moon, and they can also be used for healing, they have a power upgrade, the origin. Herbs collected during the full moon have a very powerful energy. depending on the hours and days - you can use them almost everywhere (but gently). These herbs can also contribute to conscious dreams, one can create amulets and planted at the time the plant will have a strong vibrant energy. In the Full Moon energy mix, forming a strong flow, and it is transmitted to all living things around.
C time immemorial, herbal tinctures and herbs our ancestors have done amulets. For good luck, for the battle for peace in the home, health, and envious of the wicked, from the enemies. Very often used for home obereganiya poppy, wormwood, immortelle. Among other herbs: nettle, flax, hemp - used to treat patients, to support health.
But even before the home grown mallow, which was believed to have protected the women from disease and accident of marriage (and vice versa, to lure suitors, if a married woman - built relationships in marriage).
Sunflowers also attract prosperity and a bright, sunny energy. But it can not grow under the fence.
I forgot to mention this before, but don't work with any plant until you've researched it. Many plants, such as rue or foxglove, can be poisonous if ingested and can cause contact dermatitis (nasty skin rash) if handled without protective clothing.
Despite the fact that the poisonous grass can easily lead to diseases of the brain, cause injury and even death, they were used in magic for many centuries.
The most common was their use for the preparation of the so-called "flying ointments". Those were prepared by boiling herbs in oil. This ointment is superimposed on the body (should be close to the fire). Hallucinations appeared, creating an incredibly real feeling of flight. The most vivid imagination of people attending at the time of such hallucinogenic trips.