The following is number one off topic and number two my opinion so take it or leave it.
These two things are not my opinion.
The New Testament was written for Believers.
Every epistle was written to a specific group of believers.
Everything else in this post is my opinion
Except the Gospel of John.
John 20:31
but these are written that you may believe that Jesus is the Christ, the Son of God, and that believing you may have life in His name.
That is written directly to unbelievers and it's the mission statement for the Gospel of John. When ever I'm talking to a non Christian I draw heavily from John.
That's why I referr to John 3:16 as the greatest quote(really anywhere) in the Bible