Why God chooses to use some and not others who seemingly have far greater talents and abilities has never been completely clear to me.  The fact is that God often uses individuals who have little in the natural to recommend them.  I think of Gideon, who demanded a sign from God, and Barak the military leader who wouldn't face the enemy unless a woman went with him; Rahab, the prostitute, who was of the lineage of Jesus Christ.  Include the twelve who were common fishermen, farmers, tax collectors and laborers, who walked with Jesus... along with St. Augustine, Mary Slessor, the Scottish lass who left such a mark on Africa in the nineteenth century, and on and on.  But two common threads seem to be evident:  Men and women who are used by God in some measure or capacity are people of simple faith, and have lives characterized by complete obedience.