The problem witth a teacher though it is nice to have one, is that they will teach from their bias prospective. Now please do note, that bias is not to be used in a negitive context. What I am saying, is that each person has a different worldview. Whether is be based on religion, morals, politics, and so on. So because of this what a teacher will teach you will not be a universal truth, but rather their prespective. So having more than one teacher is often advised if you go that route.
But honestly, as has been stated, you are your own best teacher. Books written by different authors will be very helpful. They will all write from their experiences and viewpoints giving you a rainbow of different perspectives. Some authors I would recomend that I am very fond of are Donald Michael Kraig and Scott Cunningham. There are also many good articles written on here my favorites being by Personified and Lark. For other websites I am personally very fond of Theoi.com it has information about Greek deities.
Though it is important to note a few quick things; Wicca is a religion, not all Wiccans are witches. Witchcraft is a practice that not all Pagans do. Pagan is a blanket term just as Christianity is. There are many different variations. Witchcraft can be done with no religion at all. So you do not have to perscribe to any. Though your worldview will effect how you cast, and what you cast. You do not have to be Wiccan to believe in the concept of karma, though not everyone does in the first place.