A disciple must follow the teachings of Jesus Christ. A true disciple must follow what Jesus Christ teaches. That is what a true disciple does - he follows the teachings of his master. The Lord Jesus Christ is our Master. He is the one who teaches us all things. We are following what He is teaching us. Anyone who claims to be a disciple but do not follow his master's teachings could best be described as a rebel. It is a rebel who refuses to obey the instructions of his master.
When we are talking about disciples of Jesus Christ, they are not only the twelve apostles. No, the disciples are not only the twelve apostles. The twelve apostles were the pioneer disciples. They had been with Jesus Christ during the time he was living and walking in this earth as human. We should listen to the apostles because they have learnt from Jesus Christ himself. They were taught by our Lord. They the true custodians of the mysteries and the teachings of Jesus Christ. They are not the only disciples that Jesus Christ had.
The Lord Jesus Christ commanded the disciples to go into the world and make all men His disciples. That means that they are many more disciples apart from the twelve apostles. The twelve apostles are those who received the doctrines of the church from our Lord Jesus Christ. When they pass them on to us, we who have received the doctrines will become the disciples of Jesus Christ also. So, anyone who follows all the teachings of Jesus Christ will become the true disciple of Jesus Christ.