Mt 4:13-16, Isa 9:1-2, Mt 4:17,23, Mt 9:35, Mk 1:39, Lk 4:15,43-44, Mt 4:18-19, Mt 10:6
Jesus preached the gospel in Galilee. Gentile Galilee was a region primarily inhabited by mixed Jews. The Jews despised the Jews of Galilee. In other words, Jesus preached the gospel to lowly people. In the Old Testament, it was foretold that Christ would preach the gospel to Galilee. (Mt 4:13-16, Isa 9:1-2)
Mt 4:13 And leaving Nazareth, he came and dwelt in Capernaum, which is upon the sea coast, in the borders of Zabulon and Nephthalim: 14 That it might be fulfilled which was spoken by Esaias the prophet, saying, 15 The land of Zabulon, and the land of Nephthalim, by the way of the sea, beyond Jordan, Galilee of the Gentiles; 16 The people which sat in darkness saw great light; and to them which sat in the region and shadow of death light is sprung up.
Isa 9:1 Nevertheless the dimness shall not be such as was in her vexation, when at the first he lightly afflicted the land of Zebulun and the land of Naphtali, and afterward did more grievously afflict her by the way of the sea, beyond Jordan, in Galilee of the nations. 2 The people that walked in darkness have seen a great light: they that dwell in the land of the shadow of death, upon them hath the light shined.
Also, Jesus preached the gospel of the kingdom. The content of the gospel of the kingdom is that Christ has come. (Mt 4:17,23)
Mt 4:17 From that time Jesus began to preach, and to say, Repent: for the kingdom of heaven is at hand. 23 And Jesus went about all Galilee, teaching in their synagogues, and preaching the gospel of the kingdom, and healing all manner of sickness and all manner of disease among the people.
Also, Jesus preached the gospel mainly in the synagogue. The synagogue is a gathering place for those who believe in Judaism. He opened the Old Testament to the Jews. (Mt 9:35, Mk 1:39, Lk 4:15,44)
Mt 9:35 And Jesus went about all the cities and villages, teaching in their synagogues, and preaching the gospel of the kingdom, and healing every sickness and every disease among the people.
Mk 1:39 And he preached in their synagogues throughout all Galilee, and cast out devils.
Lk 4:15 And he taught in their synagogues, being glorified of all. 43 And he said unto them, I must preach the kingdom of God to other cities also: for therefore am I sent. 44 And he preached in the synagogues of Galilee.
The key to Jesus' evangelism is finding disciples. (Mt 4:18-19)
Mt 4:18 And Jesus, walking by the sea of Galilee, saw two brethren, Simon called Peter, and Andrew his brother, casting a net into the sea: for they were fishers. 19 And he saith unto them, Follow me, and I will make you fishers of men.
Jesus also sent his disciples to the read sheep of Israel. This is to explain the gospel of the kingdom to those who know the Old Testament but do not understand it accurately. (Mt 10:6)
Mt 10:6 But go rather to the lost sheep of the house of Israel.
In conclusion, in order to save people, Jesus first found His disciples, went to those who knew the Old Testament first, and opened the Old Testament, telling them that Christ came and that Christ is Himself.