I do not know details, but here is my two cents.
I have seen with my own eyes, new people come into the church and blend right in as if they've been there for years. It is doable.
The hint has already been given by Acts 5:41. If you are genuinely interested in people, and show it by your comments and questions, they will know. This cannot be faked.
Example: "I heard your daughter was sick. How is she doing?" "I heard your son just graduated. Congratulations!" "Did you get that job you wanted?" "Do you need some help with that?"
If the focus is on them, and not yourself, people will talk. If you appear at ease with yourself, people will feel more at ease with you. If you feel confident and comfortable, it will show. I you don't, people will pick up on it.
Also, there are times when someone can appear foreboding or standoffish, and I am surprised to find that the person is not like that at all. Looks are deceiving.
If I were you, I would remain at your good Bible believing church that feeds you the Word. To make friends, show yourself friendly.
I think in many cases a person is not comfortable, for whatever reason, and the vibes are picked up by others. Do you tend to feel inferior for whatever reason? Do you feel different, for whatever reason? (Answer this in your own mind.) Check out your own inner voice that directs you, and you may find the thing you need to change.
The focus should be "others", not on "self" in a social setting. It works. People respond to people who are interested.
Jesus saith unto him, "I am the Way, the Truth and the Life; no man cometh unto the Father but by me." John 14:6