Describe the geography of Luke's Gospel.
This is a very insightful question. Not many people ask about the geography of the gospel of Luke. Let me make a few points that will help you think through this issue.
First, it is important to know that Luke and Acts should be read together. They were put on different scrolls only because of limitations of space on a piece of papyri. When you realize this, you will see that there is a very important geographic pattern.
Second, the gospel of Luke starts with a universal emphasis. For instance, Luke ties the birth of Jesus to the Roman emperors. Luke 2:1 and 3:1 mention Caesar Augustus and Tiberius respectively. After the birth narratives, Luke 4-9 has Jesus in Galilee. In Luke 10-19, we see the ministry of Jesus in Samaria and Judea. Finally, we see Jesus in Jerusalem and we have the passion narrative. (Luke 19-24). We can say that there is a narrowing from the universal to the particular - the death and resurrection of Jesus.
Third, in the book of Acts, we see the opposite pattern. Acts 1:8 is the programmatic verse and the rest of the book follows this geographic pattern:
But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.”
Notice that there is a chiastic pattern - the particular to the universal. The ends of the earth is the focus at the end of the book of Acts.