While I do not claim to be an official Wiccan (more of a fan-girl, really) I’ve learned many valuable lessons from the father and mother of Wicca: Gerald Gardner and Doreen Valiente. The most important of those lessons were gleaned from their lived example.
What I learned from Gerald Gardner
Gerald Gardner (1884-1964) is known as the father of British Initiatory Wicca, bless him. The way I see it, the best lesson we can learn from this Grand Old Man would be our sovereign right to eclecticism and syncretism.
What is this blasphemy, you ask?
We know for a historical fact that Gardner had an extensive and wandering occult education in magick folklore and mythology, before he was (allegedly) initiated by the witches of the New Forest coven at the age of 55.
He was clearly influenced by the Rosicrucian Theatre folks he met there, with whose members he formed a coven.
He lived in Malaysia and Borneo his entire career which explains the influence of Eastern philosophies.
He was a Co-Mason, and was granted a charter to the Order Templi Orientis (OTO) directly from the most famous dastardly bastard of the occult™, Aleister Crowley. We know that Gardner had access to Golden Dawn Ceremonial Magick material, with all their western occult influences of Hermetic Philosophy and Qabalah, alchemy, astrology, theosophy, theurgy, etc. Garnder’s rituals heavily lifted from Crowley’s written works.
What became “Wicca” was Gardner’s special blend of assorted occult teachings, mixed with what he knew of British folk witchery and ancient paganism – oh, and his adoration of Margaret Murray’s highly problematic anthropological work. His personal affinities for naturism are woven into Wiccan practice, too, resulting in the practice of “Skyclad” ritual nudity.
We can assume that what he and his coven came up with worked well enough for them, so they shared it with others. I’m really glad they did. This system we now call “Wicca” took off across the globe like wildfire, which tells me that it was the Will of the Old Gods that it come into being and be practiced. That’s how the old Gods work, in my experience.
What I learned from Doreen Valiente
Doreen Valiente (1922-1999) was the high-priestess for Gerald Gardner’s coven for a time, and was an accomplished occult scholar and poet. It is primarily Doreen we may thank for the current forms of sacred poetry which inspire Witches today, such as “The Charge of the Goddess,” “The Witch’s Creed,” and “The Witch’s Rune.” She didn’t like the heavy hand of Aleister Crowley haunting those early Gardnerian rituals, so she edited and augmented the Book of Shadows from her own knowledge and artistry.
Turns out Gardner was, himself, a dastardly bastard of the occult™, and Doreen and half the coven laid down the law to stop him from speaking to the press without permission, thus breaking their oaths of secrecy, and endangering their members. When Garner tried to replace Doreen with a younger, and more easily manipulated priestess, she quit his coven in a blaze of righteous glory. Best yet, she told him exactly where he could shove his freshly-penned “ardanes.”
She then joined Robert Cochrane’s Clan of Tubal Cane, the rival gang of Traditional English Witches in the 1960’s. Cochrane turned out to be just as dastardly and when he wouldn’t stop making violent threats about his hatred of Gardnerian witches, she quit his coven too. She told him exactly where he could shove his “night of the long knives.” 
I just love it when Mama Doreen dropped the mic.
Moral of the Story:
The Grand Old Man taught me the most important lesson of witchery, by example if not by creed: If he could cobble together the bits and pieces of occult lore that helped his coveners live spiritually fulfilled lives, then we can do the same. However, I’ll also learn from his mistakes, and be forthcoming about my sources. I can admit loudly and proudly that I am an Eclectic Witch. I also learn what NOT to do from Gardner’s example, so I won’t break my oaths of privacy and discretion, especially when it would endanger my coven-mates.
I’m mostly grateful to Doreen for teaching modern Witches that we CAN improve upon our liturgy and rituals, no matter who wrote them originally. We can each lend our skills, talents, and knowledge to improve our practices. We can grow up a bit, see the errors of past ways, and progress the Craft with integrity. And when the dastardly bastards™ among us attempt to control, manipulate, or drag us all down into their petty dramas and ego-strokings, we can exit stage left. We are free to go forth into the night and do better, our own way.
 Phillips, Julia. “History of Wicca in England: 1939 to the Present Day.” http://geraldgardner.com/History_of_Wicca_Revised.pdf, 2004. Accessed October 3, 2018.
 Valiente, Doreen. Rebirth of Witchcraft.