The gift is the whole statement.
2:8 faith; and that not of yourselves. “That” refers to the entire previous statement of salvation, not only the grace but the faith. Although men are required to believe for salvation, even that faith is part of the gift of God which saves and cannot be exercised by one’s own power. God’s grace is preeminent in every aspect of salvation (cf. Ro 3:20; Gal 2:16).
John F. MacArthur Jr., The MacArthur Study Bible: New American Standard Bible. (Nashville, TN: Thomas Nelson Publishers, 2006), Eph 2:8.