We begin with Mark 16:9-20. Mark's emphasis is mission as "Preaching the Gospel to all Creation.
Most versions of the Bible will have a variation on the following sentence just before Mark 16:9. "The earliest manuscripts and some other ancient witnesses do not have verses 9–20." This is true and it does seem that these verses seem to be a mish mash of the other commissions, however, because it is in harmony with the rest of Mark's gospel I think we can take this as Scripture and learn from it.
9 When Jesus rose early on the first day of the week, he appeared first to Mary Magdalene, out of whom he had driven seven demons. 10 She went and told those who had been with him and who were mourning and weeping. 11 When they heard that Jesus was alive and that she had seen him, they did not believe it.
12 Afterward Jesus appeared in a different form to two of them while they were walking in the country. 13 These returned and reported it to the rest; but they did not believe them either.
14 Later Jesus appeared to the Eleven as they were eating; he rebuked them for their lack of faith and their stubborn refusal to believe those who had seen him after he had risen.
15 He said to them, “Go into all the world and preach the gospel to all creation. 16 Whoever believes and is baptized will be saved, but whoever does not believe will be condemned. 17 And these signs will accompany those who believe: In my name they will drive out demons; they will speak in new tongues; 18 they will pick up snakes with their hands; and when they drink deadly poison, it will not hurt them at all; they will place their hands on sick people, and they will get well.”
19 After the Lord Jesus had spoken to them, he was taken up into heaven and he sat at the right hand of God. 20 Then the disciples went out and preached everywhere, and the Lord worked with them and confirmed his word by the signs that accompanied it.
There are some important elements to highlight here. Firstly, the mission in Mark is described as "preaching the Gospel". Mark begins his Gospel with these words, "The beginning of the Gospel of Jesus the Messiah, the Son of God" (Mark 1:1). Clearly for Mark the Gospel or the Good News (grk euanggelion) is very important. Jesus comes preaching good news.