For the early Christians, what did they use for a Bible? Did they maybe have one or two Gospels, and that's it? As far as written materials, did they carry around an Old Testament? Was a lot of the religion based upon rote memorization of stories, that were then repeated and taught to others, with no actual written documents?
I suppose it depends on what you mean by "early Christians". When Paul was wandering around the place, there was no mention of St. Paul ever reading from established books. In the mildly humorous story of the young man who went to sleep because Paul talked "on and on", and fell to his death as a result, it's obvious that Paul was just talking, and talking, and talking ...
But not reading.
His letters no doubt followed over a period of time, as he gained experience in the churches he travelled to.
I suspect that in a church dependent on oral tradition in it's earliest stages, Creeds would have been important, since they formulated the faith in a simple and succinct form, which could be easily memorised.
Pauline letters and the Gospels probably began to slowly circulate around the churches as time went on, since writing was hard work back then. It's easy today with computers and word processors, but very time consuming in those days.
So the short answer is we don't know just how the earliest Christians practised or formalised their faith. None of the earliest references to Christians either by themselves or their enemies seem to make reference to what we might call the New Testament or even specific books of NT Scripture.
Christ may have read from a scroll of Isaiah in a Jewish synagogue when He announced that "Today this Scripture is fulfilled in your hearing", but that was in a Jewish synagogue which had a well established literary tradition behind it, unlike the earliest Christian churches.
The earliest Church didn't have a Bible, yet it had authority granted to Peter and the Apostles by Christ himself, which was only recorded in Scripture as it was formalised at a later date.
The Petrine authority was admitted by St. Paul who made the comment that "When Cephas came to Antioch, I opposed him to his face, because he stood condemned", thus admitting Peter's authority even as he rebuked him. If Paul didn't recognise Peter's authority, he would hardly have bothered to mention Peter by name in this particular event.
To wit, the tradition of Petrine and apostolic authority preceded the New Testament Scriptures.