I dun really know much abt rank increment. But generally, the
pay structure depends on your vocation.
Combat vocations are definitely higher i guess. My ns csm once
told me, as he used to be a regular, he asked cmpb which vocation
has the highest pay. They told him commandos, then he asked...2nd
highest - armour. So he joined armour. But beware...once armor
always armor.