I have yet to meet someone that that does not think about gaining promotion at work. Even those who are completely incompetent in their jobs still long for promotion! Amazingly you and I can testify to the fact that many incompetent people hold positions for which they are not qualified.
The second thing I would say is that many times as believers we may doubt whether God is actually interested in our work. In fact we call our work “secular”. We fail to understand that anything a holy person does, in line with God's will is actually an holy act. When Paul was making and selling tents in Acts 18 was that secular or holy? Therefore if our acts are holy our work life is holy, then God is interested in what we do and how we do at work.
Speaking about being capable; there is no reason why a believer should be incompetent at work. I do actually believe that we ought to be the best in our workplaces; positioned as good colleagues; good manager and good workers.
The Bible has a lot to say about being promoted and how somebody can begin to excel in the workplace. The Bible says humble yourselves therefore under the mighty hand of God and in due season he will lift you up; also another scripture says that promotion does not come from the east or the west but that promotion comes from God.
God is always interested in promoting his people. You just need to remember the story of Joseph to understand that God wants us to excel even in difficult times. Joseph was a man in slavery at Potiphar's house; yet he excelled in his job. Even when he went into prison, he still excelled and God used those circumstances to promote him to next in command to Pharaoh.
One thing for sure; God wants us to be blameless and spotless at work so that our promotion will not draw undue negative attention and thereby misrepresent Christ.
As long as we are diligent at work and trust God for our needs promotion will definitely come.