Paul on Level of the Big Three

Galatians 2:6 And the leaders of the church had nothing to add to what I was preaching. (By the way, their reputation as great leaders made no difference to me, for God has no favorites.) 

These leaders with the big reputation were most likely the three apostles listed in vs. 9, James, Peter and John.  These men had nothing additional to add to what Paul had been shown by God.  By saying they had nothing to add, Paul puts himself on the same level as these men. This position validated Paul as an apostle himself. Paul got revelation straight from the horses mouth, Jesus, and did not need any help in understanding the gospel.