Following the teachings of the Lord Jesus Christ is what makes a person a disciple of Jesus Christ. You can't be the disciple when you do not follow the doctrines of Jesus Christ. When you are not obedient to the doctrines of Jesus Christ, then you are not his disciple.
It is not only the early apostles who are the disciples of Jesus Christ. Those of us who truly follow the teachings of Jesus Christ are also his disciples. We are his disciples when we do what he commands us. Of course, we know that a disciple is a follower of a master. We are not disciples if we have no master which we are following. We are the followers of Jesus Christ and must follow his teachings.
Obeying some of God's commandments and refusing to obey some won't make us true disciples. We are true disciples when we are able to obey all of God's commandments. When we follow the teachings of Jesus Christ totally we can be called true disciples.