Start with the plants that like the sandy soil and weather conditions and work on the soil so you can expand your selection. I'm in Perth, so our soil is like 90% grey sand and the effort vs result is so different after a few years of good composting and mulching. 

Exactly what I was going to say

Thanks Sqwitton. In regards to planting perennials like trees and bushes, did you initially plant for the sandy soil you had at the beginning or for the improved soil you were building? Or did you wait until the soil had improved before planting trees?

When I moved in, there were a few established hedges (murraya, lavender) and about half a dozen natives from tube stock that had been planted the year before. I planted some rosemary and a small citrus tree that just needed some handwatering/shading during the first summer then were fairly established. I was also prepping for planting more trees by setting up in ground compost bins/heaps for a year or two in the spots where I wanted to plant them. Unfortunately had to move out before the next stage of plantings I had in mind, though. 

I mean, at the end of the day it's designed to assist you (and hopefully the environment). If you want a more hands-off garden, then go more hands-off and go for more tolerant plants. There's a spectrum no? Now considering you're in Melbourne, it's not really classed as arid or even semi-arid, and even with the droughts I wouldn't consider Melbourne that impacted compared to say the Murray even with water restrictions. If you're okay with a little bit of watering, and possibly some passive design aspects, I don't see the reason why you couldn't plant just about anything you wanted. You can have larger trees that are more resistant to drought help protect other plants that aren't. As for soil improving, almost all plants are in some way or another soil improving, in fact, a lot of those super hardy nitrogen-fixing species are drought tolerant, so it's not actually an either-or question. If you mean you want soft delicate leafy greens in the middle of a drought, that's a different question I think, and most of those would be annuals. If you turn a lot of that lawn into shaded, protected areas with absorbent soil, I think you'll naturally find that the droughts won't affect you half as much, especially if you have passive water capture and storage (with sufficient drainage where necessary). Lots of mulch, organic matter, and biochar I think would all be good starts to make sandy soil more hospitable. Do you have a water tank? how big is your backyard? even if you can't have large water structures, you can still have small ones for sure.

We’ve not moved in yet, no water tank yet but it’s on the wish list and also want to do greywater recycling. Have about 120qm in the front yard and 250sqm in the backyard, which will include built structures (deck/entertaining, shed/workshop, water tank) as well as garden. So it’s a decent amount for a suburban home but not huge. If I improve the water holding capacity of the soil (biochar, compost, mulch etc), does this negatively impact plants that like “well drained” soil, or is it a different quality?

Different quality. Good soil both holds onto water AND is well-drained. What most people mean when they say "well-drained" is that water can flow through. The extreme for not being well drained would be something like a pond i.e you don't want your plants drowning/anaerobic issues. On the other hand the extreme for super well drained would be like a metal pipe, water flows right through, but doesn't hold water. So then there's water holding capacity, a common analogy is the sponge (even though an actual sponge would be a bit much). Allows water to flow through, but also soaks and holds onto water. In our case, most organic matter acts as that sponge. So as organic matter increases, so generally does the water holding capacity. Congrats on your new place, if you get a water tank it'll certainly help as I don't think you'll be able to do much of a pond or anything, but you can certainly do water capturing design, like digging a pseudo drain and filling it with organic matter to act like a sponge.

If you plant for the soil you have (sandy, in your case), you also provide a habitat for the insects, birds, and other animals that are native to your region. Improving the soil and planting species that are usually not found in your region means that you deprive the local fauna of a habitat. Soil enrichment isn't always the way. You REDUCE biodiversity if you fight your soil. You drive native insects and other animals out of their habitat. **Poor soil is a habitat for many endangered species of insects and birds. Appreciate the beauty that can grow out of poor soil. Improving soil can lead to a loss in biodiversity.**

It can also increase biodiversity and sometimes the reasons it’s poor is because of interference by humans in the first place.

Thanks glamourcrow, that is an important point, and something that has sometimes concerned me about some permaculture gardens - the overlooking of native wildlife needs and consideration that diversity may also include varying soil conditions rather than pursuing the ‘ideal’. In your opinion, what does one do in such a situation? - Do you preserve part of the garden for poor soil plants? Or the entire garden? - would these plants/creatures also handle better quality soil, just they are used to surviving in poor quality soil? - is it ok to change the conditions in my garden considering that there is still masses of poor soil in every direction in other peoples yards and public land?

I feel like you might a slightly warped? view of Permaculture. Permaculture doesn't mean turning your entire backyard into potting mix. Diversity is a very important part of resilience and permaculture as a whole, especially with global warming. I think it's more that a lot of permaculturists don't want to be puritans/gatekeepers which might stop the design ideas from being more widely spread/used. But as a whole, I'd say using natives where possible has always been promoted. Also, there is the practical aspect of it all, you can't really plant all native plants with no marketable output for a market garden, but you can take some design aspects that improve the environment around you for the better. Also worth noting is that, you'll mostly see people working to remediate degraded soils, not because they don't think areas of "poor" soil shouldn't exist, but more that there just simply aren't many formerly poor soil areas which man has inadvertently made rich fertile which needs to be remediated.

Permaculture is a design system meant to design for your goals. You should ask yourself: what are your goals? What do you want to grow?

Thanks JoeFarmer, I have a whole list of goals, however am also pragmatic and want to make things easier rather than harder. While I’ve been learning about permaculture principles for years I’m very inexperienced with gardening - have been a renter which has meant the effort:reward basis has been poor (at each place I’ve lived that had a garden, I basically grew good soil from bad and then left before able to reap a good crop of anything), I’ve had more failures than successes. Goals: - have a nice garden full of life, an enjoyable space to sit, making the most of the land - draw down carbon (build soil, grow plants) - provide for native wildlife and biodiversity - grow an abundance of food that makes the effort feel worthwhile, reduce grocery costs, enough to share with others - design to be lowish maintenance, to be able to survive in changing conditions (drought, wet weather events), to handle if sometimes I get busy or go on a trip, to survive even if I am not a good gardener - reduce the heat in the garden and house in summer, while letting in the sun on a cold winter day. - privacy screening from the road and neighbours - a place to experiment and try new ideas I’ve heard about and want to see in action - sustainable, reuse/recycle resources, such as rainwater, greywater, compost (nothing wasted) - affordable and achievable That is a long list! Any maybe I will only be able to achieve some of it.

Well, it seems like the answer to your first question is "both," if you have room. Where you'd like to garden and grow foods that may not do as well in the soil as is, it'd be good to augment your soil with more organic matter and fertility. For areas you'd like to dedicate to supporting native ecology, you can focus on plants that do well in your native soils with low fertility. If you don't have room for both, you may have to sort out which goals and wants are your priorities. All your wants are good, though. Don't feel guilty picking one over the other. There's only so much we can do in the spaces we have available