Faith means faith in surrender to Krishna
After reading Bhagavad-gita one should promptly come to the conclusion of Bhagavad-gita: one should give up all other engagements and adopt the service of the Supreme Lord, Krsna, the Personality of Godhead. If one is convinced of this philosophy of life, that is faith.
Bhagavad Gita As It Is 9.3 purport