The gospel of Jesus Christ is the “good news” of the “coming kingdom of God” which is synonymous with the “coming salvation”.
This was prophesied and first announced after Jesus was imbued with the Holy Spirit (Mk. 1:1-25;Matt.3:2). Jesus needed this in-dwelling of the HS and the Father’s pronouncement identifying him as “my beloved Son, in whom I am well pleased”(Mk.1:10-11). Jesus is the rightful “messenger” of the gospel of God the Father.
This “gospel of Christ” manifests the “power of God(Father) unto salvation to everyone that believes”(Rom. 1:16). This gospel is about “how salvation comes about”.
This power of God the Father shows us how to “enter” the Kingdom of God, meaning how to be saved. “unless your righteousness exceeds the righteousness of the scribes and Pharisees, you will by no means enter the kingdom of heaven” (Matt. 5:19, 20). The “righteousness of God” is the “righteousness of faith”, by faith “of” Jesus (Rom. 1:17; 3:21-31; 5:1), who started it; He is the “author and finisher of our faith”(Heb. 12:2). And, this faith of Jesus continues “from faith to faith”(Rom.1:17). Meaning, we have to have faith in Jesus and by extension, faith in the promise of God the Father
Notice that the “kingdom of God” is still future, “the kingdom of God is near” (Lu. 21:31). Similarly, salvation is still future. While we are “saved by faith”, it only means the mechanism of how we are saved and not the “actual salvation” itself. Salvation is about “being” in the “kingdom of God”. How so?
Remember that everything is about the faith “of” Jesus who started it all. But, faith in whom and in what? Faith in the Father that what was promised to Creator YHVH ELOHIM (Logos, Jesus) will be fulfilled. And what was promised?
Looking back at Genesis narrative, God the Father was the Creator of and “purposed” all (Heb.1:2; Eph. 3:9-11), although creation was done actually by the Word/Logos or YHVH ELOHIM(Almighty God; Heb. 11:3) who incarnated into man-Jesus. The original plan was “purposed” by the Father (Eph. 3:11).The Creator God knew that created human beings, Adam & Eve, and for that matter all mankind, would sin against him. Mankind therefore has to be reconciled to the Father.
The “covenant” between the Father and YHVH ELOHIM/Creator Logos was for man to be “kingdom of God”. And for this to occur the Creator Logos has to incarnate into man-Jesus, die for mankind as a “reconciliation” event. Reconciliation did not actually “save”us, but positioned us to the state of Adam before he sinned. Having been reconciled, the “dead Jesus” would be resurrected to life so that we “shall be saved by his life”(Rom. 5:10); “shall” meaning not yet and still future”.
What has this resurrection of Jesus accomplished? Being alive, he can then “go to the Father” and receive the “promise of the Holy Spirit” to be sent to us (Jn. 16:7). The Holy Spirit is a “must” as the “flesh is weak”(Mk.14:38), and needed “re-doing like a Potter to marred clay” (Jer. 18:4;Heb. 2:6; Ps.8:4).
The in-dwelling of the HS in us, will “seal, sanctify, guide, teach, and give us power” to have the “mind of Christ”(Rom. 12:2; Phil. 2:5-11;2 Tim. 1:7) and “conformed in the likeness of his Son Jesus”(Rom. 8:29). Yes, we shall be like “his Son”(I Jn 3:2-3), different from each other and unique, yet “one”(I Cor. 12:12;Rom. 12:4).
Taking the Genesis creation of man into consideration, God has initially created an “image and likeness of YHVH ELOHIM”. This “image” however was just a “temple or template” for the Holy Spirit to in-dwell after first in-dwelling in Jesus at the river Jordan. Eventually, God planned for mankind not to stay as “an image” only. Instead, we will be like him in spirit-body, “put on immortality”, “one with him” as the “future world” will not be subjected again to angels but to us (Heb. 2:5).
This is the “gospel/good news”, the plan of “salvation”, for us to be in the “God-kingdom”, not in the “plant-kingdom”, nor the “animal kingdom