If you want to get up the ranks as an officer, you would need at least a bachelor's degree; I think you can't be promoted higher than the rank of Major if you don't have a degree, but I could be wrong. Most, if not all, of the officers in the Australian Army now who are of high rank have uni degrees.
You can do anything except SSO roles (docs, engineers, etc.) and combat roles (as you're a lass) with your degrees, so you can join Intelligence, Logistics, Signals, Medical (as a Medical Corps officer), Aviation etc. depending on how you perform at RMC Duntroon. Remember that the education requirements for a GSO are just a pass in the HSC, so degrees don't really mean much unless if you want to get promoted high up.
Anyway, best bet is to talk to a recruiter, or to call up your nearest Army Reserve unit. They should help you out with everything.