Sit down some afternoon — maybe today — and look up all the “kingdom” references in the New Testament and you will see the following major ideas:
First, kingdom refers to a redemptive society. Second, one must “enter” this redemptive kingdom society by repentance and faith and obedience to Jesus. Third, kingdom society and Jesus are so closely connected one has to say that there is no such thing as “kingdom” apart from relationship to Jesus. Fourth, no one uses the word “kingdom” in the NT for “social” justice that is not connected to kingdom people of Jesus or connected to the fellowship of his followers — the Church.
The best example of “kingdom” work in the entire Bible is Acts 2:42-47, and there the kingdom people, in the context of a local fellowship (church), were making the kingdom manifest. The place to begin with kingdom work is to take care of the society of Jesus’ followers.