Paul in his letter to the Ephesians tells us about the fullness of God and this fullness that the Bible tells us about consists in a love: "and to know this love that surpasses knowledge - that you may be filled to the measure of all the fullness of God." Ephesians 3:19. This love surpasses our knowledge, that is, it is a grace, a charism: "I became a servant of this gospel by the gift of God's grace given me through the working of his power", Ephesians 3:7; and this love comes from the wisdom of God: "His intent was that now, through the church, the manifold wisdom of God should be made known" Ephesians 3:10. This love is also a mystery, that is, it is something that is not evident, that must be revealed: "Surely you have heard about the administration of God's grace that was given to me for you, that is, the mystery made known to me by revelation, as I have already written briefly.", Ephesians 3:2-3.
The mystery of the fullness of God is to be wise as God is wise: "Be perfect, as your heavenly Father is perfect", Matthew 5:48; is to be full of the holy spirit: "Who is wise and understanding among you? Let them show it by their good life, by deeds done in the humility that comes from wisdom.", James 3:13.
And this fullness is fundamentally a mystery that comes from the love and wisdom of God because it is in us as a potential: the potential of the seed is the tree that bears fruit, the potential of the worm is the butterfly. Jesus compares the Kingdom of God with a hidden treasure, with something that is in us and must be discovered:"The kingdom of heaven is like treasure hidden in a field. When a man found it, he hid it again, and then in his joy went and sold all he had and bought that field.", Matthew 13:44.
The fullness of God is adulthood, but this adulthood is reached through progressivity, spiritual gifts are progressive, that is, they are way because we grow, the Kingdom of God is like leaven that ferments: "The kingdom of heaven is like yeast that a woman took and mixed into about sixty pounds of flour until it worked all through the dough.", Matthew 13:33.
The fullness of God is manifested in us, in the fruits of the spirit, which are the ultimate ends of human life and the traits of God's character: "But the fruit of the spirit is love, joy, peace, forbearance, kindness, goodness, faithfulness, gentleness, self-control. Against such things there is no law.", Galatians 5:22-23.