God makes two people.
One He makes confident, filled with business savvy and the ability to speak in public. He follows God's guidance, and ends up the CEO of a major company, earning half a million dollars per year, and living in comfort and ease his entire life.
The second person, God makes shy and introverted, but with a beautiful heart for compassion and personal study. He ends up being a hospital chaplain at a tiny poor town, giving endless compassion to those who are suffering. But he leads a poor life, with frequent worries about money and where his next meal is coming from.
Is God unfair? Both were made in a certain way, and led to certain careers; Both are fulfilling God's will. And the nonbeliever says, "God isn't fair."
The reality, however, is that God is fair...but our life here on fallen Earth often isn't. In the area that really counts--fulfillment of God's plan for their lives--both men are equally successful. And both will receive equal praise and eternal reward for their faith, these two brothers in Christ.
But our fallen world has chosen, for whatever reason, to compensate people unfairly. Extroverts make more money than introverts. Men make more than women. Sociopaths are statistically more likely to be promoted in companies. Teachers, firefighters, and policemen struggle to get by, while hedonist NBA players make millions per year and argue for more.
We are so financially focused in our determination of success that it has become almost impossible for us to really internalize the fact that God grades using different criteria than our fallen world. Our world measures success in different criteria, and rewards using different methods, than does God.
It is critical that we realize this. Following God's will may make one person richer than the other--that does not mean God is unfair, it means our fallen world is unfair. Some people are born in areas of the world that suffer greater than us in America--that does not mean God is unfair, it means that the rulers in those lands are unfair. A church teaching a Christless Christianity may explode and experience massive growth (both in people and money), while a small, truly Godly church stagnates and dies--that does not mean God is unfair, it means we people on fallen Earth are unfair.
Always reminder yourself of this fact. God does not judge as people judge. God does not reward as our world rewards. He uses an entirely different grade-book. And rest easy...one day God makes all this inequity undone.