Read Romans, chapters 9 and 10. Paul spells out very clearly the steps we all must follow to be in right standing with God.
Paul said: "I am made all things to all men, that I might by ALL means SAVE some." (We must be diverse to reach the lost!)
He also told us to not judge others in what they eat, what they drink, and what days they may observe. (there is a certain liberty that comes from being saved, and that involves choosing how and where we might serve).