The Gospel is about Jesus' Specific Work and It is Not the Whole Bible
Believe Jesus died for our sins in accordance with the Scriptures, was buried, God raised Him from the dead on the third day in accordance with the Scriptures, and He was seen afterward by Peter, the Disciples, over 500 brothers at once (most of whom were still alive when Paul wrote to the Corinthians congregation this formulation of the gospel that he was taught), and then Jesus was seen by James, then the Apostles, and then by Paul. Believing these things, call on the name of Master Jesus Christ for your salvation by verbally confessing Master Jesus. 1 Corinthians 15:1-8 and Romans 10:9, 10, 13
So, that's the gospel (according to the Scriptures). Let's stop using the word "gospel" to refer to half of Theology and in a general way. This salvation doctrine is what IT is, and there are support background information attached to it throughout the Bible, but those things (such as creation and even that we are sinners) is not THIS, the method of salvation, the good news of those specific actions of Christ's work and immediate aftermath. It's not His earthly ministry (He was under the Law until He died; see Romans 6-8).
THE - this - Gospel is hardly mentioned in churches around where I live, even in the rare instance when salvation doctrine is mentioned. There's something desperately wrong with the diffusion of it on the one hand (by using the word "gospel" to mean arbitrarily anything and everything in the Bible) and the multiple versions of its specifics on the other hand ("repent and be baptized", for instance, was a response to the Jews who just got through badgering Pilate to murder their long-awaited Messiah and King, and they were to repent of that specific sin and be baptized in the way they normally used that symbol, which was prevalent for a wider range of meanings than the strange way some of us have made it into an absolute necessity for salvation, due to the simple lack of reading the context around that phrase, "repent and be baptized"; we DO repent when we believe and confess - not confess sin, but confess Master Jesus, which is the very opposite of confessing sin). Do I need to continue in order to prove that we are messed up concerning the gospel? The gospel is simple and specific. Many people don't want to believe those things or confess Master Jesus with their mouths in order to call on His name for their salvation. Defend the gospel, Church, to the glory of our same Master and Savior Jesus Christ, and He will make us glad in Him, indeed, with a clarity concerning deeper things in our Church culture and in Theology and in straight righteousness (which we get, according to Romans 10:9b-10a, from believing the Resurrection!).
Knowledge of our sin nature, as found all the way back at our beginnings in Genesis, is fundamental to knowing what it means that Jesus, who didn't sin, became sin for us and died for our sins as a substitutionary atoning sacrifice to God's justice, but it's what Jesus did that's the point of the gospel and not what we did, so we can't stop with knowledge of sin and it's tragic ending of death, but we must - must - call His work for us "the Gospel".