in whom we have our redemption through his blood, the forgiveness of our sins, according to the riches of his favor
in whom we have our redemption - Throughout the Old Testament, the people who God would redeem were the Jews. Paul says here that God redeems those in Christ - even if they are Gentile.
- Ephesians 1:7
through his blood, the forgiveness of our sins, - The Jews were accustomed to the blood of animal sacrifices covering their sins, but here Paul points out that it is the blood of Jesus that provides forgiveness for our sins.
according to the riches of his favor - Normally one would redeem something with some sort of monetary payment but just like the Jews were not redeemed with money, neither are the Gentiles. It is by the riches of His favor that we are redeemed. This is also in contrast to the expectation that glory and riches (glory is addressed in Eph. 1:6) would come to some Jews when the Messiah would come in the Day of Destruction. God's favor would not bring glory and riches but rather, glory and riches is His favor itself!