The Kingdom of God was Jesus’ curriculum for practicing the better.  Every word and act of Jesus was a revelation of some aspect of that Kingdom. We can see this in the light, life, and love which came through everything he said and did.
Jesus’ light overcame the darkness, first by exposing the darkness of empire in his prophetic ministry. This put him on a collision course with the imperialistic political and religious leaders, and it led to his crucifixion. But for light to come, darkness has to go. We see this particularly in his healing ministry and in his offer of forgiveness as the darkness in people was replaced by the light.
The illumination was life giving. People “came alive” when they heard him teach, saw him minister, and personally experienced his healing and forgiveness. Jesus made good on his promise to give abundant life to everyone, and he did not withhold it from anyone. The phrase that he “ate and drank with sinners” is the telling phrase to show the full measure of his acceptance of all and his offer of grace to everyone. The common people rejoiced, the political and religious leaders were enraged.
His inclusivity angered those who lived with an in/out mindset and whose spirituality enabled them to pray with thanksgiving that they were not like “those other people” (Luke 18:11). They grumpled in the early days of his ministry and went on from there to look for ways to entrap him. When those efforts failed, they conspired to kill him. Darkness and death do not applaud light and life.
All of Jesus’ instruction was aimed to establish love in individuals, groups, and the world. That was/is the essence of the Kingdom, summarized in the two great commandments. When Jesus said he came to fulfill the law and the prophets (Matthew 5:17), he meant “filling them full” with what had largely drained from them: the love of God and neighbor. 
He did this through his own demonstration of love to others, which John summarized by writing, “Having loved his own who were in the world, he loved them fully” (John 13:1). And when he told his followers to be lovers, he gave them the means to do so–“remain in me” (John 15:4), and the model to follow–“as I have loved you. ”
Light, life, and love–the main elements in the Kingdom of God (fleshed out in numerous sub-topics and multiple expressions). Light, light, and love–the inauguration of the new covenant and new creation (restoring and continuing God’s original intention). Light, life, and love–what it means to practice the better.
 My favorite book about the Kingdom of God is by E. Stanley Jones, ‘The Unshakable Kingdom and the Unchanging Person.’. George Eldon Ladd’s book, ‘The Gospel of the Kingdom’ is another good resource.
 Walter Brueggemann deals with this re-filling in a powerful way in his book, ‘God, Neighbor, Empire.’