The gospel is Jesus Christ himself, what He did on the cross and what He does in and through us. Everything that Christ is, and all that He did are the best news anyone could ever hear in this life. There is not and there will be no good news for us, in this life, which could be compared with the gospel of Jesus Christ. This is true, since there is nothing that could be compared with Jesus Christ.
You might wonder, why is good news, what He did and who He is the Christ unto us? Well, all that He is and all that He did, He is and He did them all, for us. The gospel is good news for us is not good works from us. It is not what we do, but what He did. A preaching that tells us to become and do for God is not the preaching of the gospel of Jesus Christ. Such preaching is only necessary so we may realize our lack and our inability to be and do what God requires from us. We should never think that we could ever meet the requirements of God, since such a thought would lead us to despise the gospel of Jesus Christ. You see, the good news is that Jesus Christ is for us what we could never be.Also He did for us and does through us, what we could never do. If we think that we can meet the requirements of God, then there is no room in us for the gospel.
God loved us and gave to us His Son Jesus Christ. This is the pure gospel. If we add or subtract something from it, we will distort it. It might look like it, but will not be the true gospel of Jesus Christ.
Faith and acceptance of the gospel is the only thing we can do, nothing else. Jesus Christ was given by God the Father, that we might believe and receive Him, nothing else.