When I was at GAM, the adelaide boys and girls were working the hardest in terms of flight hours per annum. The upshot is that when you start out as casual you start flying/earning money straight away as those Alice runs through the middle of the night are usually done by the casual pilot. In oher bases the casual had to wait till someone was ill or went on leave before getting a day of work.
In the current market however, it shouldn't be very long before you get a full-time slot because GAM have always had a high turnover of pilots.
Pay is as per the award on salary if full-time, as a casual you get a daily rate. When full-time, you'll work 4/5 days a week usually.
GAM a great company when I was there, haven't heard that change over last year......but remember bankrunners have a shelf life of maybe 2 years because after that you'll be well and truly burnt out.
Good luck and enjoy the experience