The word 'Gospel' means a good news. And this was summarized in verse 4. '[Jesus] gave Himself for our sins, that He might deliver us out of this present evil age, according to the will of our God and Father.' And God is the one who raised [Jesus] from the dead (v.1), whom be the glory forever and ever (v.5), and who called [them] by the grace of Christ. This is the gospel which brings peace to those who have faith in Jesus. And this gospel is perfect in a way that there's nothing that we can add (contribute).
If we add something to the gospel, it is the different gospel, which is not a good news (gospel). The type of different gospel was legalism and humanism, and can be prosperity gospel. These different gospels do not give all the glory to God, because they seem to make people contribute the salvation. It is from the desire to control therefore people like and follow this different gospel. How to prevent from following these false gospels is focusing and investigating the true gospel. By knowing more and more about the true gospel, we can distinguish the different gospel which brings curse, not peace.
1. EM Cook-out tomorrow at noon at Mr. Eugene's house.