How do I know if I am explaining the depth of the gospel or adding to the gospel? The answer is found in discovering the content of the earliest preaching, the central themes that appear in gospel presentations.
What we would need is something that touches on all the central items the gospel seeks to proclaim, the things that would have been believed and received when the “word” was preached. We would want it to include the things that appear over and over again in the early speeches of Acts, that ground the teaching of the Apostles in the rest of the New Testament, and that encapsulates what “the word of His grace” was meant to include. And since baptism dramatically displays the gospel, it would need to include all the major truths being proclaimed in that moment as well.