I highly encourage the following: 

1. Read Scot McKnight's The King Jesus Gospel.

2. Check out Tim Gombis' insightful series of posts on The Gospel of the Kingdom, pt. 1, 2, and 3.

Gombis hits the nail on the head here:

Over the last several months, I’ve had several conversations about how the Gospels’ language about “the gospel” should shape how Christians conceive of the gospel.  Whereas the New Testament mainly envisions a broader announcement of a larger reality, many evangelicals associate “the gospel” with a brief presentation, or information about the mechanics of an individual transaction that can secure divine forgiveness and the establishment of a personal relationship with God.

The Gospel is more than a checklist, more than a five-minute "yes-or-no" conversation in which you can make a new Christian... its a narrative of cosmic significance. If God really is reconciling all things to himself in and through Jesus Christ, then everything we do and say, ESPECIALLY when we're speaking of the Gospel, must change.