Which Church? Which doctrine? These are a few questions that are grappled with for someone seeking to join a church. However, this should be kept in mind:
When King Jesus was here on this earth he was asked about his doctrine.
“Jesus answered them, and said, ‘My doctrine is not mine, but his that sent me. If any man will do his will, he shall know of the doctrine, whether it be of God, or whether I speak of myself. He that speaketh of himself seeketh his own glory: but he that seeketh his glory that sent him, the same is true, and no unrighteousness is in him’” (John 7:16-18).
There is only one doctrine: The gospel of the word of God and the testimony of Jesus Christ. “For there is one God, and one mediator between God and men, the man Christ Jesus: who gave himself a ransom for all, to be testified in due time” (1 Timothy 2:5–6).
The house of God is not in physical buildings with different names, “But Christ as a son over his own house; whose house are we, if we hold fast the confidence and the rejoicing of the hope firm unto the end” (Hebrews 3:6).
“For we know that if our earthly house of this tabernacle were dissolved, we have a building of God, a house not made with hands, eternal in the heavens” (2 Corinthians 5:1).