The New Revised Standard Version of the Bible tells us that "gospel" comes from the Anglo-Saxon "god-spell" and means "good news." The New RSV Bible also explains that: "Gospels are not biographies. They are accounts of the life and teaching of Jesus, but they are also testimonies to Jesus and what faith in Christ means for the world. Each of the gospel writers wanted to say something specific about the meaning of Jesus and carefully selected materials and arranged them. The gospels contain a great deal of historical information, but that information is always interpreted by the writers to show Jesus as Son of God and Savior of the world."
None of the gospels in the New Testament identifies its author, so the names given each are later attributions in the life of the early church. Tradition held that the gospel of Matthew was the first gospel to be written, but today it is generally thought the gospel of Mark was written earlier than the other gospels of the New Testament. So, I suggest beginning with the gospel of Mark and, quite quickly, we will see why it not only seems to be the first gospel but also is the basis for the gospels of Matthew and Luke.