The foundation of our Christian faith is Jesus Christ the son of God. He is the author & finisher of our faith :
looking unto Jesus the author and finisher of our faith; who for the joy that was set before him endured the cross, despising the shame, and is sat down at the right hand of the throne of God. Hebrews 12:2
There can be no Gospel message or preaching without the story of the sacrifice of Christ as the Redeemer of mankind. But something has happened to the integrity of the Gospel of Christ over time, it has become diluted, twisted, contaminated, etc.
We will find the true gospel in the Scriptures. The following verse is called the ‘Gospel in a nutshell’:
Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain. For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures 1 Corinthians 15:1-4