What does God want from us? To put it succinctly: nothing. God wants nothing from us. Or, more properly, God wants nothing. Period.
What does this mean for us? First off, I suppose I should explain what it means when we say God wants nothing. When we want, we desire a good we do not have (it may come with evils, but all desires are for something fundamentally good, be it happiness, fellowship, etc.). God is goodness itself, and thus there is no good he does not have. Therefore he cannot want.
So if God wants nothing from us, why are there all these rules, guidelines, etc.? Why is there Christianity if God gains nothing from our worship? Why is there anything if God alone has everything he needs?
God created the us for our sakes, not for his own. He created us to give us the chance to love him, to experience good, to live life most fully. Thus, as Irenaeus said, “the glory of God is man fully alive.” What God wants from us (to use incorrect but helpful language) is for us to be most fully human, because then we can most fully enjoy all the benefits of his infinite goodness.
And so to be a Christian is to be really human. The Christian, simply put, embraces true life wholly and utterly, becoming more and more truly the image and likeness of God himself. This is one’s vocation.