What department do you want to apply for as an army staff officer?
If you take an examination of a military school from a local place, your eyesight is not too high, just above 4.8. Staff officers belong to the administrative category, that is, the command category you mentioned. The technology is stable, easy to popularize and has great administrative power. If you are willing to spend money or find relationships, your promotion will not be slow. I suggest you take the administrative examination.