The very first thing
There is a principle in Bible study called the first mention principle. It says that the first time something is mentioned in the Bible is a precedent that must be factored into interpreting subsequent references. What is the first thing the Bible says? "In the beginning God created the heaven and the earth (Gen 1:1)." This shows us several vital things. Creation had a beginning. One way this is discussed is called the Kalam Cosmological Argument. It says that every effect has a cause, so if you keep going back you must arrive at a first cause. The universe has a beginning, so the only logical first cause is God. Atheists cannot explain where matter, energy, laws of nature, information, and other things originated, but the Bible explains it in the first verse. God created. The only alternative is that nothing created everything. This issue also illuminates a major flaw in the atheistic worldview. They say the universe and everything in it came to be through random, unguided processes, but then they talk about a world of laws and order. They do the same thing with societal issues. They say they believe in laws and morals, but they have no foundation in their worldview for them.
This is why creationism, especially young earth creationism, is attacked so intensely and barred from the "scientific" community. It is foundational to a proper interpretation of scripture and therefore a Biblical worldview. When we understand that God is our Creator, we know that He has the right to make the rules, and that we are accountable to Him. We understand that He is the source of truth and not us. He is the heavenly Father and provider, and we are not independent of Him. If you hit a building with a projectile, you can do damage, but the building can still stand. When you attack the foundation, the whole building can be destroyed.
The early church in the book of Acts was initially all Jewish. Although they were not perfect, there was a strong culture of Biblical knowledge. They had synagogues all over Israel and even the world. When the apostles started to preach after they received the Holy Ghost in Acts 2, their messages were to Jewish people. They quoted Messianic prophecies from the Old Testament to show people that Jesus is the Christ. As persecution hit the early church, they went to other places to preach. However, they still stuck to preaching to Jews in the synagogues (Acts 8:1-4). Then Saul who was persecuting the church was converted (Acts 9). Although he did not fully understand it yet, his main ministry would be to Gentiles (Acts 9:15, Acts 22:21). Although Philip preached to Samaria and baptized the Ethiopian eunuch (Acts 8), and Peter preached to Cornelius and his household (Acts 10), it was still mostly a Jewish church evangelizing other Jews. Even these examples are of people who were already familiar on some level. The Grecians mentioned in Acts 6:2 were most likely Hellenized Jews, not Gentiles. The Ethiopian eunuch in Acts 8 was a proselyte and even had his own copy of scriptures. Peter said Cornelius already knew about the word (Acts 10:37). He was a devout man of prayer and almsgiving who had led his whole house to God (Acts 10:2). At first, Paul went from city to city and preached in the synagogues (Acts13). He continued the pattern of quoting scriptures since the audience was familiar with them.
Then Paul went to Lystra and encountered a wholly pagan culture with no familiarity with the scriptures (Acts 14:6-23). After they saw a miracle, they were preparing to honor Paul and Barnabas as pagan deities. Paul restrained them. It is noteworthy what he said to them. He did not quote verses from the law of Moses forbidding idol worship. He said, "Sirs, why do ye these things? We also are men of like passions with you, and preach unto you that ye should turn from these vanities unto the living God, which made heaven, and earth, and the sea, and all things that are therein: Who in times past suffered all nations to walk in their own ways. Nevertheless he left not himself without witness, in that he did good, and gave us rain from heaven, and fruitful seasons, filling our hearts with food and gladness (Acts 14:15-17)". He introduced them to their Creator and provider. The next recorded public message in the book of Acts was Paul in Athens (Acts 17:22-31). Athens was full of various pagan religious beliefs and altars to idols. Paul's opening statement as he introduced the true God to them was "God that made the world and all things therein, seeing that he is Lord of heaven and earth, dwelleth not in temples made with hands. Neither is worshipped with men's hands, as though he needed any thing, seeing he giveth to all life, and breath, and all things (Acts 17:24-25)". He started out with the fact that God made everything and is our provider. He concluded with the statement that we are all accountable to Him (vs 30-31). Paul saw few results.
The original headquarters of the early church was Jerusalem (Lk 24, Acts 1-15). However, after a church was started in Antioch north of there in Syria (Acts 11), and after Barnabas brought Paul there it became a center of evangelism to Gentiles (Acts 13). After that point, the focus of the rest of the book of Acts shifts from Peter and Jerusalem to Paul, Antioch, and his three missionary journeys which were all launched from there (Acts 13-20). The Lord Jesus had prophesied the destruction of Jerusalem and had warned His disciples (Mt 23:37-39, Mt 24:1-2 & 15-21, Lk 21:20-24). He told them that when they Jerusalem surrounded by armies to flee because it was about to be destroyed, and they did. The church became more and more Gentile. The challenge then was for these Gentile Christians to maintain their Christian culture and Biblical worldview when surrounded by those who did not. Paul was continually warning them not to slip back into the pagan ways of their past and their surroundings. Sadly, within a few hundred years, the churches we read about in the New Testament were mostly gone. Thankfully, the apostle's doctrine continued throughout the centuries in many places.
Current Western culture is much more like the people of Athens in Acts 17 than the people of Jerusalem in Acts 2. Although the Jews were not perfect, they had an underlying familiarity with the scriptures which allowed the apostles to use them in their preaching. The people of Athens had never heard of the true God or the Bible. It was all strange to them. Paul did not quote one scripture to them. He even quoted their own poets. This is not to say we should not quote scriptures when preaching. It is quite the contrary. However, Paul said that he adjusted his approach depending on his audience to attempt to be successful (1Cor 9:19-23). There used to be a general familiarity with the Bible even among those who did not actively practice the faith. Now there is such a dearth of basic knowledge of the Bible, not only does the general population not know the Bible, many Christians have a dangerously low level of knowledge of the scriptures. One reason so many have failed to dedicate themselves to the study of the Bible is because there has been so much doubt cast about its validity, even from its opening verse. We need a revival of faith and knowledge of the Bible starting from the beginning to the end. Western civilization was founded on the Bible. The reason it is fading away is that people have largely abandoned it. The only thing that can save it is a return to the book it is based on.