During the ages before Penticost priests, kings, and prophets usually had oil poured over their heads symbolizing that God was going to use that person for a specific purpose. It was a visible way to show them and everyone else that God was entering into a close relationship. God would enter that person. The person would have special gifts and insights into God. Those gifts were used to help others.
Now, starting at Pentecost with those who heard Peter preach and believed the gospel, God saves through the washing of rebirth and review by the Holy Spirit (5b). The Holy Spirit pours into those who believe in Jesus Christ our Savior (6). We become heirs having the hope of eternal life. We are anointed with the Holy Spirit.
God gives gifts. He calls, He anoints with the Spirit. He makes his people priests, kings, and prophets. All this is grace. My response is to be careful to devote myself to doing what is good (8).