The single most important fact about God is that he made all that is our universe, including us. The entire gospel rests on this fact and develops from it.
Whether we encounter the gospel of Jesus as children in church or in a presentation from an enthusiastic Christian, we may only absorb a few pieces of the whole thing.
The Apostles' Creed lays out all the basics in a short outline, and is affirmed by almost every Christian church in history.