From Christopher Wright's The Mission of God's People:
And that reign of God, inaugurated by Jesus and indeed embodied in him, continues to work within human history in ways that Jesus said it would - like seed growing, like yeast rising, like fish being caught. The kingdom of God is at work in and through the lives of those who have 'entered' it, that is, in whose lives God is reigning through repentance and faith in Christ, in those who are committed to the ways of Jesus Christ by submitting to him as Lord, in those who seek first the kingdom of God and his justice, in those who hunger and thirst for justice.
In short, the reign of God is found among those who understand their mission, to make peace, to do good, and to proclaim God's salvation. For those are the things, as Isaiah's gospel messenger called out, that constitute the good news that 'our God reigns'. The gospel is good news about God, as a foundation for all that makes it good news for us.