This is probably pretty close to what I would say if somebody asked me.
The gospel is the good news of what became of the son of God. And what became of the human race in him. Baxter Kruger
He died, we died. He rose we rose, he ascended we ascended. We sit at the right hand of the Throne of God, we are the righteousness of God in him
The gospel is Jesus with us as the fathers Eternal son as one anointed in the Holy Spirit and the Creator and sustainer of all things.
John 1:3 (ESV) 3 All things were made through him, and without him was not any thing made that was made.
Matthew 6.6 