The central tenets of Gnosticism are the polar opposite of the central tenets of Christianity. And no one here has stated the “equal to or greater importance than what you read in the Bible” that you refer to. None of the apostles had the Bible though. And none of Jesus’ early first century followers had the Bible either. The Bible didn’t even exist until the 4th century. But there were a lot of Jesus followers in the meantime...and their relationship with the Savior was likely just as valid as yours is.
