I have been reading a book called the "New Organic Grower" by Eliot Coleman.
The New Organic Grower: Master's Manual of Tools and Techniques for the Home and Market Gardener (A gardener's supply book)
There are some recommendations for starting to grow food on bad soil and also for successive applications. I am unable to give you Eliot's full instructions as it may infringe copyright so you will have to buy the book. The book refers to the use of "Green Sand" which is a sand containing many useful minerals including Potash. I am unable to find any references on the internet to "Green Sand" in Australia so I would recommend the use of volcanic rock dust as an alternative. If anyone in Australia does know about "Green Sand" or perhaps it has another name then please let me know.
Many people are using raised beds, lining them with plastic weed mats (Not something I do or would recommended) and then adding soil mixes from landscape supply companies. There are a few problems relating to this, some of which which may not become apparent for a couple of years. A Raised bed with a liner is basically a large pot and the garden mix most people are buying is compost (potting mix). This will work quite well for around 18 months (This goes for pots too). Potting mix and garden soil are quite different. Potting mix, as previously mentioned, is compost (rotted organic matter) and garden soil (Earth) contains organic matter and minerals which come from our rocks. As soil gets older the minerals deplete (unless maintained by nature or us). You cannot keep growing food in the same spot year in year out without feeding the plants/soil. Growing plants takes the goodness from the soil and needs to be replaced. Many conventional farmers do not feed the soil and feed the plant directly using chemical fertilisers. I choose to feed the soil which in turn, feeds the plant. I could spend several hours explaining how to feed soil and long term solutions for feeding the soil but we can do that another day or you can read a million books on the subject.
The following is a plan for getting soil working well enough to grow good quality food.
For the first year add manure/compost, Soft rock phosphate & Rock dust.
After that use green manures and compost to maintain it as best as possible to reduce you inputs and costs.
You can also do it differently by adding the Soft rock phosphate & Rock dust to a working compost heap so it is already broken down before it gets on the ground.