“May grace and peace be multiplied to you in the knowledge of God and of Jesus our Lord.”
This verse is pronouncing a blessing. It is conveying the blessing of God through the knowledge of God. The knowledge of God in Christ is the exclusive source of this blessing. Specifically, this knowledge is communicated through Christ. Philip (John 14:8-9) saw and knew God because he saw and knew Christ.
This promise of blessing is personal. The Triune God is a personal God not an abstract deity. He is a God who can be known and desires to be known. We cannot know him exhaustively, but we can know him truly and that is where our comfort as his people lies.
It is also an expansive blessing. In the knowledge of God, the blessing of grace and peace is not added, but multiplied. There is always more of God to be know and more of his blessedness to be enjoyed. Much more.