can you practice Wicca, as in crystals and herbs and stuff, and be christian?

Wicca has nothing whatsoever to do with Christianity, and in fact, is in opposition to Christianity. Wicca, also termed Pagan Witchcraft, is a modern Pagan religion. Scholars of religion categorise it as both a new religious movement and as part of the occultist stream of Western esotericism. Its traditional core beliefs, principles and practices were originally outlined in the 1940s and 1950s by Gardner and Doreen Valiente, both in published books and in secret written and oral teachings passed along to their initiates.

i dont believe that Wicca is an established occult practice in any of the times of church of Jesus Christ. however, there are many that believe in Healing and the use of herbs for medicinal purposes.

when comparing witchcraft, with the 9 biblical definitions, including one that is called sorcery, and then comparing alchemy and biological chemistry and even some practices of Aromatic and incense smells, a person might be stepping on unknown definitions of prohibitions.

that said, if there is wiccan idolatry, no one can drink of the cup of the devil or of a demon and think they can claim to be a christian nor a jew or even a muslim. and there is idolatry in worshiping deities that are NOT God the Heavenly Father and accepting Jesus as Lord and savior.

that said, one should compare what it means to practice the occult or the curious arts when the bible new testament says that the former saints burned their books in an act of repentance and confessing what their works of curious arts were.

why did they burn books?  see acts 15 !

on the other hand, is it wrong to learn medicine and how to make your own.  it would be great to be able to make ones own medicine if a person actually believes that medicine is part of their lives that makes them healthy. and there is a difference between making poisons and curses then there is making medicine and blessing someone.

there is another new testament verse that defines two kinds of peace.  one that comes from above, like from heaven and from Jesus, where He himself distinguishes the difference between what comes from man and what comes of God. its also said that Jesus taught his disciple how to "cure" diseases. not just feed people pills and hope for the profits of selling them. its also noticeable that Simon the sorcerer came to peter and desired to purchase the Holy Ghost. and yet Peter said to him, that his money should perish with him.  the Holy Ghost is given by the laying on of hands and then the gift of the holy ghost is different than just having the spirit of God. anyone can make a drug, that makes you happy. but i know drugs and medicines the way we have it today, are only temporary. and receiving the gift of the Holy Ghost is not temporary, except based on sinful transgressions when the holy ghost is grieved and then departs from a man. so, one has to come to revelation to know the differences between medicine sorcery and witchcraft and the art of healing, or to know what the curious arts were being repented of when the Word of God was preached among the first church and their converts.

No. Superstition is directly opposed to God's truth.

Sure but it would be like saying you are a vegan that eats steak on the weekend.

Do you think the mud that Jesus put on the blind man's eyes is what healed him?

Yes, you can. But there's more to healing than any stuff.

Catholicism is the One True Faith and a person can know this with certainty by reciting the rosary every day with care and sincerity.

Um, not so much.