Was Marian devotion commonplace among early Christians during the first centuries of Christianity? What about the first century AD? What about the second century AD?
Marian devotion grows into progression secretly, as Mary gave an instruction to the gospel writers not to mention Her, but only put some key events in Her life as revealed to Mary of Agreda.
The first Apostle who encounter the need for devotion to Our Lady was Peter, as he learned directly from the "Another Advocate" how to console a fallen soul who betrayed their Lord. Jesus promised Peter that his faith will not fail, so, in turn he can confirmed his brethren, who will also fall or betray Jesus whom they professed an oath during the Last Supper to serve, but all the Apostles who made an oath hide in fear, only Peter was courageous enough to follow but he failed miserably. But, this is part of Divine Providence to allow Peter to know who will be the advocate if Jesus will be gone, as he reminded them. that He will not leave them orphan, the "another Advocate" is a Mother.
But I have prayed for thee, that thy faith fail not: and thou, being once converted, confirm thy brethren.(Luke22:32)
Peter after experiencing how to be consoled from the Theotokos, was able to rise-up again, and in turn Peter consoled or confirmed his brethren. Peter then, fulfill the words of Jesus Christ to his brethren Apostles. This is the key, why Judas was not able to rise-up because, he did not seek the help of the Theotokos unlike Peter.
This was Mary the Theotokos, showing Peter Her "new role" to them, A Mother, Helper, Teacher, Consoler, Comforter and an Advocate.
This role was played by Mary at the Upper Room, teaching the Apostles and Disciples to do a Cenacle Prayer to prepare their hearts and minds, to receive the gifts and anointing of the Holy Spirit, in which Mary is both a Mother and a Teacher to the Apostles and Disciples.
Did Mary teaches the Apostles? This was the tradition teaches by the Eastern Orthodox Churches.
The highlight of Mary playing the role of the "another Advocate", Helper, Consoler or Comforter happened in 40AD, when St.James the Great experienced despair over his mission in Spain,and Mary showed Her role to him by the now recognized first Marian Apparition while Mary was still alive, its called the Our Lady of the Pillar.
https://udayton.edu/imri/mary/o/our-lady-of-the-pillar.php
So, Peter and James experienced first hand how to consoled. How about, St.John the beloved? St.John lived and cared for the Theotokos, and he experienced first hand how to contemplate God, and St.John become one of the great contemplatives surpassing Peter who can hear the voice of the Abba Father clearly, as Jesus praises him for saying...
Peter's Confession of Christ
…15“But what about you?” Jesus asked. “Who do you say I am?” 16 Simon Peter answered, “You are the Christ, the Son of the living God.” 17Jesus replied, “Blessed are you, Simon son of Jonah! For this was not revealed to you by flesh and blood, but by My Father in heaven.…(Matthew16:15-17)
So the Apostles after the experienced of the apostles Peter and James, and John the Three Pillars, now painted the new role of the Theotokos, as the "Advocata Nostra" in 50AD, and the painter was St.Luke.
Every image of Our Lady comes with a title that reveals a particular aspect of her love and intercession for her children in need: Our Lady of the Rosary, Mother of Perpetual Help, Mother of Divine Grace, Spouse of the Holy Spirit, etc. A list of her images and titles gathered from all over the world may number in the thousands, but the oldest known image is said to date back to the first century, originating from the Holy Land or Syria. It is an icon that, tradition tells us, was painted by St. Luke himself in encaustic, an ancient painting technique with hot wax and resin. Brought to Rome to save it from destruction during the iconoclasm of the Eastern Church, it is a treasure that has been hidden away for centuries. Although the fragile linden wood icon is now worm-eaten and crumbling, the face of the Blessed Mother remains, and it is exquisite! She is known by a very unusual name — the “Advocata Nostra,” Our Lawyer.
Our Lawyer? It may seem an odd title; however, the name “Advocata” or lawyer is most fitting. Mary, as Spouse of the Holy Spirit the Advocate, undoubtedly received even greater gifts of the Holy Spirit as she prayed in the midst of the Apostles at Pentecost, she herself becoming an advocate for the children of God.
https://www.themarianroom.com/a-hidden-icon-of-mary-the-advocata-nostra/
How about the first century Christian devotion to Our Lady? The first century Christian have devotion to Our Lady with devotion to Her calling Her, "Mary Help of Christian "...
There are two inscriptions from the first centuries of Christianity in Greek related to the Virgin Mary: : θεοτοκος (Teotokos, Theotokos, Mother of God) and βοηθεια (Boetheia, the Helper). The Fathers of the Church referred to Mary as "βοηθεια". John Chrysostom used the title in a homily of 345, Proclus in 476 and Sebas of Caesarea in 532. After the Patristic period (5th century), other persons used it like Romanos the Melodist in 518, the Patriarch of Jerusalem, Sophronius in 560, John of Damascus in 749 and Germanus I of Constantinople in 733.
In the view of Rev. Johann G. Roten, SM, the invocation of Mary as Help of Christians is part of the oldest prayer addressed directly to Mary, the Sub tuum praesidium, which was found on a papyrus dating, at the latest, from the end of the 3rd century. Praesidium is translated as "an assistance given in time of war by fresh troops in a strong manner."1
https://en.wikipedia.org/wiki/Mary_Help_of_Christians
The second century...to be continued..this is getting too long..
But, we can see that devotion to Mary started first after Peter experiencing Her role as Consoler, Comforter and Advocate.And followed by the experienced of the Apostles and Disciples at the Upper Room, and then by St.James the Greater, and the role of Mary being the "another Advocate" was purposely not written in the sciptures as Mary of Agreda revealed, because it will hinder the Apostles in preaching Jesus Christ as most if not all people will be more interested in Mary's role in the salvation of man.