If your char wants to make career he'll go straight to the academy, trying to graduate as young as possible and go to the most dangerous areas, political or physical, in order ot ptove himself and make promotion. If he wants to be somewhere specific, like engeneering, he'll go to university. If you're a major in Xenosociology chances are higher of getting a post in the diplomatic branch, and so on. But in general, if you're a brilliant engeneer, you'll make it as high as head of military research, but not higher, while if you're a career navy you can get as high as admiral, in theory.
It's up to you really
It's up to you really