What are the three stages in development of Gospels?

1) Words and acts of Jesus, adapted to current audience; 2) Way Apostles & others preached these things, with adaptation of wording to audience; 3) some individuals under inspiration wrote down part of this basic preaching:this is the Gospel. So the Church has something more basic than Gospels, its own ongoing teaching. What method of study builds on what we just said? Form and Redaction criticism tries to find at which of the 3 stages our present text was formed, and so find out some things. Can be useful, often is abused.