Every human should live for God's glory
If God made us for his glory, it is clear that we should live for his glory. Our duty comes from his design. So our first obligation is to show God's value by being satisfied with all that he is for us. This is the essence of loving God (Matthew 22:37) and trusting him (1 John 5:3-4) and being thankful to him (Psalm 100:2-4) It is the root of all true obedience, especially loving others (Colossians 1:4-5).