I reckon the gospels were written when the Apostles appointed Stephen and the guys to watch over the tables.
Acts 6:4 Context
1And in those days, when the number of the disciples was multiplied, there arose a murmuring of the Grecians against the Hebrews, because their widows were neglected in the daily ministration.
2Then the twelve called the multitude of the disciples
unto them, and said,
It is not reason that we should leave the word of God, and serve tables.
3Wherefore, brethren, look ye out among you seven men of honest report, full of the Holy Ghost and wisdom, whom we may appoint over this business.
4But we will give ourselves continually to prayer, and to the ministry of the word. 5And the saying pleased the whole multitude: and they chose Stephen, a man full of faith and of the Holy Ghost, and Philip, and Prochorus, and Nicanor, and Timon, and Parmenas, and Nicolas a proselyte of Antioch:
6Whom they set before the apostles: and when they had prayed, they laid
their hands on them.
7And the word of God increased; and the number of the disciples multiplied in Jerusalem greatly; and a great company of the priests were obedient to the faith.
Revelation would have been written some time between Paul's 15 day visit to Peter (around 37 AD) and 14 years later when Paul returned and John was there. (51AD).
If we allow say 10 years for the Pergamos church to be formed that would place it between 47 and 51 AD.
Of course the Pergamos church could have been formed even earlier by folks who were scattered at the stoning of Stephen.