Greetings!
To be a disciple of Christ, we must follow his word and teachings. This is the most important criteria for us to be a true disciple of Christ.
If we refused to do his teaching as believers, we are then not worthy to be called his disciples, not to talk of calling him our Lord.
Luke 6:46 And why call ye me, Lord, Lord, and do not the things which I say?
The above scripture verse is a testament that tells us that we must do his word and teachings before we can be qualified to be his disciples. If we cannot, then we cannot be seen as his disciples.
Another thing is that, not all the disciples are apostles, but all his apostles are his disciples.
Luke 6:13, 46 And when it was day, he called unto him his disciples: and of them he chose twelve, whom also he named apostles.
As we can see here, he chose 12 disciples out of the many disciples that are following him, and the 12 he had chosen are named apostles. What this means is that, he has many followers but not all his followers are chosen to become his disciple and apostles. It's only 12 of them that were privileged to be named apostles.
However, if we continuously do his word and teachings we are his disciple. The only thing that can qualify us to be his disciple is to practice his word and do his doctrine.
2 Timothy 3:10 But thou hast fully known my doctrine, manner of life, purpose, faith, longsuffering, charity, patience,
This scripture above is telling us what to do to be called his disciple. These characteristics above are all what we need to be his disciple.
Thanks for reading.