Hello everyone.
I see Peter trying to identify with his readers, to meet them on the same level. His self-designation is carefully balanced: "Servant and apostle of Christ" - he doesn't make himself smaller than he is (yes, he is an apostle, and that will become important later in the letter), but he also makes clear that he is no more than a servant of Christ, giving Christ the place of authority.
In the next sentence, then, he uses this primary authority structure between Christ and him to emphasize the equality of his readers' faith and his: "You have received faith from a gracious God, and so have I. I may have had the privilege of having known Christ personally, but before God I am still a rescued sinner just like you."
His purpose, I think, is both didactic and theological:
On the one hand he is establishing a relationship w/ his readers in which he appears not as their lord or judge, but as their coach, friend and brother. He is with them, not above them.
On the other hand, he is already teaching them: Faith is a gift from an all-powerful God to powerless people. Faith enables us to do good, but doing good can never alter our stance before God. Peter is laying the necessary foundation for what he is going to say about spiritual growth.