The scripture above informs that "righteousness, peace and joy in the Holy Ghost is the kingdom of God. What we need to note and I emphasize about that scripture is the statement "in the Holy Ghost". There's a righteousness that's not of the Holy Ghost, and there's a joy that's not of the Holy Ghost. There is a type of peace that's not of the Holy Ghost. This type of peace does not last.
Romans 14:17 shows us the Holy Ghost is a chief character in God's kingdom. If you don't have the Holy Ghost you can't manifest the kingdom, and you won't even make it into the kingdom. When Jesus Christ comes back for His people the Holy Ghost is what He will look for in people.
Jesus is the Lord of the kingdom. Colossians 1:13 The kingdom of God can be likened to a gift the Father (Jehovah) gave the Son (Jesus/Yashua). The Holy Spirit and Jesus agree 1 John 5:8
Anywhere Jesus is, the kingdom is there. When Jesus appears, the kingdom appears. Jesus is the door of the kingdom, repentance is the key to the door the kingdom. Jesus responds to repentance. The Holy Spirit is what He will look out for in people when He appears. The parable of the ten virgins prove this. Matthew 25:1-13 The virgins who didn't have enough oil in their lamps are symbolic of hypocritical Christians "who have a form of godliness but deny the power thereof" 2 Timothy 3:5 The virgins who made it with the bridegroom represent those who are not hypocritical and are genuinely watchful and have God's Spirit which is what "oil" represent in the parable.
The righteousness of God's kingdom is different from self righteousness, moralistic man-made righteousness. It is not righteousness put together to impress man or deceive people but the righteousness given by God and received by faith. Romans 3:22
There is a peace the world gives that does not last. It is flaky peace. The peace of the kingdom is stable, strong, present and helps you get through storms. John 14:27
The joy of God's kingdom is an everlasting joy the world cannot understand. It is God given joy that strengthens. Psalm 45:7
From Romans 14:17 we also see that kingdom people fast. The kingdom of God is not meat and drink. Food is a blessing, and having a good appetite is great but as kingdom people we have to learn to sacrifice food to fast as the Spirit leads.