With a high school diploma, your options are somewhat limited.
Officer, in the broadest of strokes, are the leadership responsible for, among other things, planning, preparation, and administration. Junior officers will join the fray as troop/platoon commanders, but as they progress up in more senior positions and rank, they become more responsible for commanding a desk than troops. To become an officer, an applicant either requires a university degree (DEO) or must be willing to pursue one (CEOTP or ROTP). Pay as an officer cadet attending university is about half that of a private's pay. However, the highest incentive as captain presently sits around $93,000 a year. Most officers able to qualify in their trade will eventually become captain.
NCM's, more or less, execute the will of officers. NCM's are an integral part of the command structure, but more or less fall under the command of officers. NCM's make up the meat of a troop/platoon, and as they progress in senior positions and rank, remain in the platoon structure for the majority of their careers. To become an NCM, one does not require post secondary education (but possessing one does not prevent an individual from applying and not possessing one doesn't neccessarily hinder an applicant). Corporals top out at around $56,000 a year. Most soldiers able to qualify in their trade will become corporals within about 4 years.