Being “poor in spirit”, as Jesus talks about in Matthew 5:3, is about realizing that we are bankrupt without God. When we deny the illusion that we are the masters of our own fates and confess our brokenness to God, the good news is that God is near to the brokenhearted, and where God is, there is the kingdom of heaven.
After years of proclaiming the Gospel, Paul finally goes to Jerusalem to present his message to the original followers of Jesus, not because he has any doubts himself but because he feels compelled to do so by the Holy Spirit.
In the second half of Galatians 1 Paul asserts the God-givenness of his Gospel. The bare Gospel that Paul preaches is from God and therefore needs no further refinement or augmentation by humans. This is God’s good news first and foremost.