There is nothing you can do that will please God unless you are saved by grace through faith in His Son Jesus Christ.
What God wants from us
Why was God displeased with Cain's offering?
Could it not be the condition of his heart?
It's not what you give, it's how you give it.
True worship comes from the heart.
Under the New Covenant, we serve, not out of a sense of needing to atone for our sins, but out of a sense of gratitude and love for God. (I Corinthians 15:58, Colossians 3:23)
3. Obedience (6-7)
God's rules for our behavior are there to protect us.