The Church in Jerusalem is solidly Established in the summer of A.D. 33:

While Jesus had many followers before his execution, burial, rebirth, and ascension, the nascent Church in Jerusalem was soon strongly established by His apostles and disciples who had witnessed these events.
The followers of Jesus of Nazareth were initially referred to as the Jewish sect of the “Nazarenes.”
The first recorded public act of business of the nascent church of “the Jewish sect of the Nazarenes”; the replacement of the 12th apostle:

The 11 apostles “. . . all continued with one accord in prayer and supplication, with the women, and Mary the Mother of Jesus, and with His brothers. and in those days Peter stood up in the midst of the disciples (altogether about a hundred and twenty) . . .” (Acts 1:14-15). This group of 120 Apostles and disciples remained together in Jerusalem and Peter initiated a council to replace the Apostle Judas who had betrayed the Messiah and then had killed himself.
The apostle Simon Peter proposed that a replacement Apostle be selected from the disciples of Christ present with them in Jerusalem in obedience to the Psalms which state “Let his days be few, let another take his office.” (Psalm 109:8). The process is described by Luke in the books of the Acts of Apostles. They chose two men who had been present with them “from the baptism of John to that day when He was taken up from us, one of these must become a witness of His resurrection” They proposed two men and . . . “they cast lots, and the lot fell on Mathias. And he was numbered with the eleven apostles.” (Acts 1:21-26).
The explosive growth of the church in Jerusalem on Pentecost:
On May 25th, A.D. 33 the 12 Apostles and the disciples of Jesus the Christ “. . . were all with one accord in one place . . .” when they were suddenly baptized with the Holy Spirit “And suddenly there came a sound from heaven, as of a rushing mighty wind, and it filled the whole house where they were sitting. Then there appeared to them divided tongues, as of fire, and one sat upon each of them. And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance.” (Acts 2:1-4). Jerusalem had diverse peoples present in it: Parthians, Medes, Elamites, people from Mesopotamia, Judea, Cappadocia, Pontus, Asia, Phrygia, Pamphylia, Egypt, Libya, Cyrene, Cretans, and Arabs “both Jews and proselytes” (Acts 2:7-11).
The commotion of this Holy Tornado drew a large crowd and Simon Peter addressed the crowd and explained to them that all of this (the outpouring of the Holy Spirit on the apostles and the disciples) and coming of Jesus the promised Messiah was prophesied in the Hebrew scriptures. He quoted the Books of Joel, and David, and explain how Jesus was the Christ and how His death and resurrection had atoned for everyone’s sins, “Then those who gladly received his words were baptized; and that day about 3,000 souls were added to them.“
The explosive growth of the church in Jerusalem shortly after Pentecost:

Simon Peter & John went up to the temple at the time of prayer. Peter healed a congenitally lame adult guy who had been begging at the gate of the Temple in Jerusalem for years, and who was known to all the devout Jews who regularly attended the pray services at the Temple.
This healing of a man “known to everyone” and known to have been lame all his life caused another commotion and drew a crowd, to whom Peter preached the gospel of Jesus the promised Messiah of God, and “. . . many of those who heard the word believed; and the number of the men came to be about five thousand.” (Acts 4:4). The 5,000 mentioned here only counts the “number of the men“, the number of souls added to the church would have been significantly larger.
Church Growth Requires The Establishment of Formal Church Offices:

The Apostles Established (Ordained) the Office of Deacon: The first seven deacon’s were ordained to take care of the practical day-to-day affairs and needs of the rapidly growing Jerusalem Church (Acts 6:1-5).
So it went in the summer of A.D. 33. The Jewish High Priest and the Sanhedrin had tried to squash the candle of God’s chosen Messiah, but the flame burst into a conflagration. The Jewish sect of the Nazarene was growing explosively.