Galatians 1:7-9

7 Not that there is [or could be] any other [genuine Gospel], but there are [obviously] some who are troubling and disturbing and bewildering you [with a different kind of teaching which they offer as a gospel] and want to pervert and distort the Gospel of Christ (the Messiah) [into something which it absolutely is not].

8 But even if we or an angel from heaven should preach to you a gospel contrary to and different from that which we preached to you, let him be accursed (anathema, devoted to destruction, doomed to eternal punishment)!

9 As we said before, so I now say again: If anyone is preaching to you a gospel different from or contrary to that which you received [from us], let him be accursed (anathema, devoted to destruction, doomed to eternal punishment)!

What is the Gospel? Most people believe that the Gospel is that Jesus is Lord, but Jesus did not go around and preach that He was Lord. Jesus went around and preached the Gospel of the Kingdom. What Jesus told the people was that the Kingdom of God was at hand, or available to them, Matthew 4:17.

And He went about all Galilee, teaching in their synagogues and preaching the good news (Gospel) of the kingdom, and healing every disease and every weakness and infirmity among the people. Matthew 4:23

John the Baptist also preached this Gospel.

Now after John was arrested and put in prison, Jesus came into Galilee, preaching the good news (the Gospel) of the kingdom of God, Mark 1:14

So the Gospel isn’t just that Jesus is Lord, it is that our Father’s Kingdom, which is His absolute power, has now come to man through Christ. Jesus is the only Door to our Father’s Kingdom, but the Gospel is the Kingdom and it is the power of our Father now coming to dwell within us. The Holy Spirit tells us that today this has happened for us through Christ.

For He says, In the time of favor (of an assured welcome) I have listened to and heeded your call, and I have helped you on the day of deliverance (the day of salvation). Behold, now is truly the time for a gracious welcome and acceptance [of you from God]; behold, now is the day of salvation! 2 Corinthians 6:2. 

So today we have all of the power of our Father working through and for us. Jesus is the door for the power to come, but the Gospel is the power. Today it is all our Father working through us. It is all of His grace, all of His faith, all of His love, and all of His hope that allows us to enjoy unbroken eternal fellowship with Him. Any thing that says that we have to do anything on our own, is a perversion of the True Gospel. So if someone tells you that you have to first accept, believe, or have faith for our Father to work through you is perverting the Gospel and they are operating in the spirit of the anti-christ. The Truth of the Gospel is that it is our Father who must begin and finish everything in our lives.