The straightforward reading of Colossians 1:15–20 is that Jesus is the firstborn of creation who in turn was God’s agent in creating the universe. This theme of God’s Word/Wisdom/firstborn being used by God to create everything is familiar from Jewish texts such as Proverbs, Wisdom, and the works of Philo.
Scholar Maurice Casey explains it this way:
Similar remarks may be made about Colossians 1.15-20. So much of it has static parallels from Jewish speculation about Wisdom that we must infer an author who felt that what had previously been believed of Wisdom was true of Jesus. It begins with Jesus' pre-existence and role in creation: "who is an image of the invisible God, firstbom of all creation, for through him was created everything in heaven and on earth." This description must mean that Jesus, rather than Wisdom, or as Wisdom, was the first created being (of Prov 8.22f; Philo, Qu in Gen., IV, 97). This was written centuries before Arius, when no-one believed that Jesus was the second person of the Trinity. The assertions that he was created before the world and participated in its creation were a significant advance on previous thought. They could not have been made unless it was supposed that Jesus was pre-existent, as Wisdom was perceived to have existed before the creation of the universe that she was believed to have created. Colossians 1.16-17 expands this midrashically, using Proverbs 8.22-29, and moving back from Proverbs 8.22 to Genesis 1.1.42.
Maurice Casey, From Jewish Prophet to Gentile God: The Origins and Development of New Testament Christology (1991), page 115.