For Econ, most of the G8's have great undergrad programs. However, if you are looking at going into Econ academia, I highly suggest you take as much maths as possible. Econ is one of the most maths intensive areas (similar to mathematical physics), I would recommend you do a Bsci and major in mathematics rather than doing an econ degree. Besides the standard sequence in maths, enroll in as much proof-based maths courses as you can, e.g., real analysis, functional analysis, complex analysis, measure theory, topology, abstract algebra, number theory etc. I highly recommend doing an Econ honours (not econ masters) or a MSc. Regarding PhD, I highly advise you to do it overseas in the US (preferably at a top 10: Harvard, MIT, Princeton, Stanford, Berkeley, Yale, Northwestern, Chicago, Columbia, and UPenn). The econ job market is very crowded nowadays, and unfortunately, if you do a PhD in Aus, you will most likely not find a job in the Aus job market (and you will have no chance at entering the US job market) because the market is filled with top 10 graduates; Aus PhDs are simply not competitive/prestigious enough. That said, it is extremely difficult to get into a top 10 Econ program in the US (acceptance rate is around 0.1%), you should take as much maths as possible first, and then try to do a lot of research (preferably get a publication or two), however, even then your chances are still quite slim. If you want to go into industry, however, that is a different story.