generally you will be wanting the upper end of the 80's (percentiles) or higher, but it depends on which universities you are applying to and where you live. there are significant bonuses depending on where you live. for instance, to UNSW rural applicants require much lower scores than city applicants. in addition, UWA discriminates heavily against interstate applicants, and GWS applicants get a significant umat bonus. these are just a few examples and there are quite a few more.
for UNSW, the main uni most people will be applying to, the higher your ATAR the lower your UMAT score will be. but assuming you are on your way to a good ATAR, you can be sure you'll need high 80's for an interview. if you score lower than the high 80's chances are you won't be getting interviews anywhere unless you have a very good ATAR. JCU and griffith are 2 med schools that don't require the UMAT, but you can bet competition will be extremely fierce for those two schools. JCU is very difficult to get an interview to unless you are a rural applicant or from northern queensland.
good luck. feel free to ask questions
edit: your individual sec scores don't matter too much, except at UWS where you received a scaled score (sec 3 is halved). also, UQLD will not accept any applicants into their prov med program with scores in any sec of less than 50.