To be "in Christ" means everything! To be a Christian is to be in Christ. This is why Paul could say in 2 Corinthians 12:2 that he knew a man "in Christ." He could have said, "I know a Christian." In Romans 16:7, Paul says that Andronicus and Junia were "in Christ" before he was. In other words, they were Christians before he was. Christians are those who are "in the Messiah."
To be "in Christ" means everything! To be a Christian is to be in Christ. This is why Paul could say in 2 Corinthians 12:2 that he knew a man "in Christ." He could have said, "I know a Christian." In Romans 16:7, Paul says that Andronicus and Junia were "in Christ" before he was. In other words, they were Christians before he was. Christians are those who are "in the Messiah."