Here is a quick attempt at summarising my understanding of the gospel as simply as I can. My summary is full of Christian language and there is a depth of meaning underneath concepts like 'to live in Him (Jesus)' that could be unpacked further, as could terms like 'faith' and 'repentance.' A good exercise nontheless.
The world is broken but it wasn't always broken and it won't be broken forever; there is 'good news.'
God created the world good. The centre piece of creation was humankind created in the image of God. Humankind was created to love and worship God and to live in wholeness of relationship with each other, stewarding and developing the rest of creation. However humankind broke relationship with God by disobeying God and sinning. Humanity fell short of that which God intended it to be.
As a result we all have a sin problem that separates us from God, from ourselves, from each other and from the rest of creation. In and of ourselves we are powerless to deal with this sin problem. This sin problem is wrecking havoc on earth now and separates humanity from God partially now and promises to permanently in the future.
The good news is that God in his love sent Jesus Christ to rescue humanity from sin and to deal with humankind's sin problem. Jesus lived, died, rose from the dead and sent the Spirit in order that through faith and repentance all who respond to Jesus can be forgiven their sins and from sin in order to start a new life 'in Him.'
In Him we are restored to right relationship with God, with ourselves, with each other and with the world around us. We begin the process of learning to live as God always intended us to live and do this in the context of God's community, the church. The church is historical and global in nature but also an actual, tangible community that we commit and involve ourselves in locally.
As Christ followers live missionally and participate with the Spirit in God's redemptive work, faith, hope and love will begin to change lives and communities as the rule and reign of God (his kingdom) is established here on earth as it is in heaven. While God's kingdom will only be experienced in part now, and while Christ followers are not immune to the effects of the brokenness that exits in the world, Christ followers live in light of eternity, as sign posts to the truth that Jesus Christ will return and his kingdom will be established in full forever. Justice and judgement will flow throughout the world, creation will be restored and those whose faith and trust is in Jesus Christ will be judged righteous and will live in wholeness and restored relationship with God forever.