Clarifying, debt being private debt, not so much govt, sorry my bad, but for such a large country with every resource imaginable under the sun, there should be no debt. There seems to be a general misconception from outsiders Aust. is the land of milk & honey. Hence many foreigners wish to immigrate here, but it is no walk in the park. Up to about 1985 land and housing was relatively inexpensive, no longer. https://www.finder.com.au/australias-personal-debt-reported-as-highest-in-the-world
In terms of groups, gold probably, not because it is easy to trade which I find isn't easy, but because of such a large number of stocks in XGD the gold index. This means after much homework on trading this sector, when it turns up or down I can hit the pedal to the metal and clobber it at once with good size over multiple positions which can't be done with any other sector on the asx. For example copper, I only have 3 choice positions I trade, whereas with gold I have 12 stock positions which I repeat over and over.