I did computer science, had a high enough GPA but didnt pursue dentistry right away. I worked a few years in IT then decided later to apply for Dentistry via GAMSAT and got in. The people who did BOH/Sciences had an advantage during the first half of the degree interms of knowledge, so it means...
if you want money but difficult studies then orthodontics/opthalmology
if you want easy study (its still hard) then optometry. you could open up some optom practices and if run well you could get a good lifestyle. very diffult.
undergrad - JCU/CSU
post grad - Do any undergrad, doing 1st year uni sciences helps e.g. bio/chem/physiology --> sit GAMSAT, practice essays --> get into USYD, UMelb, etc.
My undergrad was computer science and I barely passed GAMSAT using past acer tests.