The Bible references the word kingdom (347 times), the kingdom of God (97 times), and the Kingdom Heaven (45 times). There are no direct references to the "kingdom of God" in the Old Testament.
We see God’s plan unfold in the New Testament as He unveils the "Kingdom of God"
Mark. 1:15 - "the kingdom of God is at hand"
Luke. 17:20,21 - "the kingdom of God is not coming with signs to be observed... behold, the kingdom of God is in your midst"
John. 3:3 - unless one is born again, he cannot see the kingdom of God
Romans 14:17 - "the kingdom of God is righteousness and peace and joy in the Holy Spirit"
The Kingdom of Christ is all about being in relationship with Jesus, and accepting His gift of salvation. When someone enters in to Christ’s kingdom we need to be there for new believers like Paul modeled for us in his leeters in the New Testament. He showed how much he cared for them. He says in 2 Corinthians 11:28, Besides everything else (trials and hardships), I face daily the pressure of my concern for all the churches (new believers).
Be wise today and always - let God rock your world with His kingdom.