Super Esquire: Here are some examples that I've come across through my reading of the early Christian writings referencing plurality of gods teaching, prior to the great apostasy:
Justin Martyr (150 AD): "yet thereby it is demonstrated that all men are deemed worthy of becoming 'gods,' and of having power to become sons of the Highest": (Dialog of Justin with Trypho, a Jew, ch CXXIV, in Alexander Roberts, James Donaldson, The Ante-Nicene Fathers, volume I, pp 261-262)
Also here (chapter 124):
Irenaeus (c. 175 - c. 195), "For we cast blame on Him, because we have not been made gods from the beginning, but at first merely men, then at length gods . . .He (God) declares: "I have said, Ye are gods, and ye are all sons of the Highest." And also, "How, then, shall he be a God, who has not as yet been made a man? Or how can he be perfect who was but lately created? How, again, can he be immortal, who in his mortal nature did not obey his Maker? For it must be that thou, at the outset, shouldest hold the rank of a man, and then afterwards partake of the glory of God. For thou dost not make God, but God thee." (Irenaeus, "Against Heresies", Book IV, XXXVIII-XXXIX, (The Ante-Nicene Fathers, Roberts & Donaldson, Editors, Volume 1, p. 521-523)), also here:
He also wrote, "... but following the only true and steadfast Teacher, the Word of God, our Lord Jesus Christ, who did, through his transcendent love, become what we are, that He might bring us to be even what He is Himself" ("Against Heresies", Book V, Preface, in Alexander Roberts, James Donaldson, The Ante-Nicene Fathers, Volume I, p 526)
Clement of Alexandria (c. 155 - c. 220 AD): "But that man with whom the Word dwells does not alter himself, does not get himself up: he has the form which is of the Word; he is made like to God; he is beautiful; he does not ornament himself; his is beauty, the true beauty, for it is God; and that man becomes God, since God so wills. Heraclitus, then, rightly said, "Men are gods, and gods are men. For the Word Himself is the manifest mystery: God in man, and man God." (Clement of Alexandria, "The Instructor", Book III, Chap. 1, in Alexander Roberts, James Donaldson, The Ante-Nicene Fathers, volume II, p.271)
In teaching of the degrees of glory in heaven, he also teaches that men become gods. In the chapter titled "Degrees of Glory in Heaven", Clement writes: "But 'it is enough for the disciple to become as the Master,' saith the Master. To the likeness of God, then, he that is introduced into adoption and the friendship of God, to the just inheritance of the lords and gods is brought; if he be perfected, according to the Gospel, as the Lord Himself taught." ("The Stromata, or Miscellanies", book VI, chap. XIV, in Alexander Roberts, James Donaldson, The Ante-Nicene Fathers, volume II, pp 505-506).
Chapter 14 here:
Elsewhere, in his "Exhortation to the Heathen", Clement writes: "It is time, then, for us to say that the pious Christian alone is rich and wise, and of noble birth, and thus call and believe him to be God's image, and also His likeness,* having become righteous and holy and wise by Jesus Christ, and so far already like God. Accordingly this grace is indicated by the prophet, when he says, "I said that ye are gods, and all sons of the Highest." For us, yea us, He has adopted, and wishes to be called the Father of us alone, not of the unbelieving. Such is then our position who are the attendants of Christ." ("Exhortation to the Heathen", chap XII, in Alexander Roberts, James Donaldson, The Ante-Nicene Fathers, volume II, p. 206).
Origen (185-254 AD). Origen is hard to summarize, because he says so much on this topic. Here are a few examples, with brief quotations to help clue in to the relevant text:
"Now it is possible that some may dislike what we have said representing the Father as the one true God, but admitting other beings besides the true God, who have become gods by having a share of God." And " He is the God of these beings who are truly Gods, and then He is the God, in a word, of the living and not of the dead." Origen's Commentary on John, book 2 chapter 3, Ante-Nicene Fathers, Volume X, Allan Menzies, D.D., editor, (Grand Rapids, Michigan: Eerdmans Publishing, 1990 reprint) pp. 323-324.
See chapters 2 and 3 here:
And Origen's Commentary on John, book 1 chapter 34, Ante-Nicene Fathers, Volume X, Allan Menzies, D.D., editor, (Grand Rapids, Michigan: Eerdmans Publishing, 1990 reprint) p. 315.
Chapter 34 here:
He writes, "For Scripture distinguishes between those gods which are such only in name and those which are truly gods" Origen, Against Celsus, book 8.3-5, The Ante-Nicene Fathers, Vol. 4, edited by Roberts and Donaldson (Grand Rapids, Michigan: Eerdmans Publishing, 1990 reprint), pp. 640-641.
See chapters 4 and 5 here: