If you want to read the earliest extant writings, check out the sub-Apostolic fathers, that is, those who were disciples of the Apostles or of their disciples, roughly A.D. 100 to 200. What you will not find is a good deal of systematic theology, but rather very practical exhortations for churches undergoing persecution and growing and dealing with how to live a Christian life. (This is especially true of Ignatius of Antioch, whose writings are short and breathless exhortations to various churches to endure persecution and reject heresies.)
One thing that you notice immediately is that the sub-Apostolic fathers ground everything upon Scripture. Clement's Epistle to the Corinthians, for example, repeats vast amounts of the Old Testament, sometimes whole sections. Polycarp obviously is familiar with Paul, and in his Epistle to the Philippians he quotes large segments of Paul's writings, as well as the Gospels.
All of this, or course, gives the lie to contentions that the early Christians didn't know which writings were inspired. If you are familiar with the Scriptures, you will find that the vast majority of their writings are either quotations or paraphrases of what we know are Scripture.
In addition, they are mute testimony to the belief that Christ was God. How? They rarely address it because they take it for granted. If there really was disagreement in the early church, they would have mentioned it. They wrote their letters is response to the problems they saw firsthand, not to theoretical heresies yet to arise. (As an example, Ignatius takes on the Gnostics who said Christ did not have a body after the resurrection, quoting the Gospels as proof.)