The primary purpose of manifestations of the Spirit is to build up the body, the potential exists for us to use the gifts for our own benefit and that ends up bringing confusion into the mix. How we serve in the gathering (in church) should be guided by the principle of what is helpful to whoever might be in the room (outsiders are present).
1 Corinthians 14; Acts 2:1-13, 10:44-46, 19:1-10; Philippians 2:4-11