I’m neither an aborigine, nor an expert in these matters, but I’ll have a go at this.
Aboriginal “gods”, for want of a better term, can be either animal or human in form. The gods of creation are those of the dreamtime, and tend to be animal, and the human ones are ancestral or mythological beings.
The dreamtime represents the creation of the earth. As the name suggests, it happened an indeterminate age ago. The main figure from this time is the Rainbow Serpent, which is said to have travelled all over the land, leaving in its path mountains, valleys, and other landforms. Other mythical animals, reptiles, and birds also performed significant acts of creation. These acts tended quite often not to be deliberate, but as with the Rainbow Serpent, a by-product of actions they took in other matters. In possession of tremendous supernatural powers, their quarrels, loves, hunting, travelling etc all had flow on effects to the land around them.
The earth is very sacred, and most of the dreamtime creatures came from it, rather than the sky. Aboriginal people believe they themselves belong to the land, not vice versa.
The term “dreamtime” is not to be confused with “dreaming”, although the two often blur at the edges. “Dreamtime” refers to a specific religious event -ie. the creation of the universe. “Dreaming” is a more personal thing. Every tribe, every family, person, animal, or place will have its own dreaming. This involves, very generally, your own early personal history and prehistory. You dreaming might include such things as the place you were born (very important to aborigines), your name, the land your parents came from, your people’s history, your early memories, and much more.
The point at which the dreamtime slowly morphed into the reality we know is not clear, and later legends can probably fall either side of that fuzzy line. Whilst there is, in some ill-defined ways, a Greek or Roman style pantheon of Gods with rather general “ministerial responsibilities” if you like, most of the mythical beings make their appearence only once, in a given moral tale.
On the question of whether these beings react with the world in an ongoing way post-creation, I am not sure. I think people tend to call on ancestral spirits for help, rather than the creatures of the dreamtime.
At the time of European settlement, there were about, IIRC, 600 000 people living in Australia. With several ethnic groupings, many, many tribal ones, a generally nomadic lifestyle, and about 600 languages spoken, it can safely be said that there was and is tremendous variation within the aboriginal religious experience.