"And John answered and said, Master we saw one casting out devils in thy name, and we forbade him, because he followeth not with us". "And Jesus said to him, FORBID HIM NOT, for he that is not against us, IS FOR US" (Luke 9:49-50, KJV).
I believe this story answers the question you pose in this thread. "Is Church Optional" ??? In this case, a man who was apparently filled with the Spirit of God and a believer in Christ (he was after all casting out demons in the name of Jesus, which is what brought him to the attention of Christ's followers), nevertheless flat out refused to join the disciples of Christ and the Church. Was he condemned by Jesus for having sinned ? Not in the least. So who are you to judge me as a non-clerical, non-denominational Christian as not being "right" with the Gospel of Jesus Christ and the Will of God ???
Who are you to decide whom God shall choose, or in what manner a man may rightfully serve God ?! Does a clay pot argue with it's creator, (Isaiah 45:9) ??? There are more than a dozen pages in this thread, containing dozens of posts claiming a Christian must be a member of the Church in order to be right with the Gospel of Christ and the Will of God.
It is not me, who ignores the Gospel of Christ and the Will of God... but it is you my friends. As you judge, so shall you be judged.