Luke is the only evangelist who took the time to write a full history of salvation from the time of Jesus' Incarnation through the incarnation of the Church. We do not often think of his works as one continuous story but they are. For Luke, Jesus does not end with the Ascension, but lives on in his Church. For Luke, Paul does not or labor alone. For Luke, Paul does not supplant Jesus and we can clearly see that Jesus is the whole reason for Paul's mission. Many churches look to Paul alone and leave out the other Apostles who worked so hard to spread the Gospel, often with their lives. Do not be deceived - the history of the Church is the continuation of God's Creation and nothing is left behind. to do so is to miss the whole point. There is no salvation without covenant - all of them, including the gift of the Spirit.
Without Luke we do not feel the full impact of the coming of the Spirit and the effect that had on Jesus' followers and on the world as a whole. Without Luke we do not see the continued hand of God in our lives and our salvation. So do not think of them as the Gospel of Luke and the Acts of the Apostles, but as Luke/Acts. Read Paul in light of Luke/Acts and see the foundation from which Paul works.
In the first book, Theophilus, I dealt with all that Jesus did and taught until the day he was taken up, after giving instructions through the holy Spirit to the apostles whom he had chosen. He presented himself alive to them by many proofs after he had suffered, appearing to them during forty days and speaking about the kingdom of God. While meeting with them, he enjoined them not to depart from Jerusalem, but to wait for “the promise of the Father about which you have heard me speak; for John baptized with water, but in a few days you will be baptized with the holy Spirit.”
-- Luke Acts 1:1-5