At a very minimum, you have to believe what the Bible says about the person of Jesus Christ...His life, His death, His ressurection, that He is the second person in the Trinity, and that He has the power to forgive your sins.
I am the first one to point out when GGG deviates from the truth, but as a Catholic I can say that he has never called into question the faith or legitimacy of Catholics or the Catholic Church. He only disagrees with about 10% of Catholic dogma and adheres to the old Catholic view of Young Earth creation.