Congrats Bruno! How exciting for you to begin to realize your dream!
If it's possible to just observe your land for a year and see how sunlight, water, wind and microclimates all interact throughout the year, you may save yourself a lot of headaches down the road. That doesn't mean that you can't be mulching, composting, building soil with cover crops, and planting out a nursery of plants that you will use in the future. But before you make ultimate decisions about where your earthworks, waterworks, pathways, etc., will go, it's good to observe and interact with the land for a year.
I would suggest that you work in order of greatest permanence. So first, put in your swales, earthworks and pathways. Long after you are gone or after your trees die, your earthworks will out last everything else.
Think through your zones. Zone 1 is closest to your house: your herbs and annual veggies, etc. Zone 2, logically goes outside of Zone 1, but close enough that you can tend to it easily. Think about how many steps you can save if you place things in a logical spot—your compost
should be somewhere near your
chickens, your water source near your garden beds, etc. For such an urban oasis, you won't have more than zones 1, 2 and 3.
Grey water from your kitchen sink and bathroom
shower can flow naturally via gravity to orchards below. Its nice to plumb that in before things get too developed. Your gray water "system" does not need to be any more sophisticated than a simple leach line that you plumb from the house down to a fixed point lower on the land. Then you attach a hose to the end of that pipe and you move the hose around the orchard from time to time. Every drop of water counts. Use it multiple times.
If you are going to add
chickens, it's nice to have them uphill from the garden so that all that nitrogen makes it way down the hill toward your garden. Build your
chicken coop and chicken run in such a way that you can toss your compostables right into their space, and then easily sweep the finished compost up and cart it away after a few weeks. It's tougher to use a chicken
tractor on a hilly site, but you can still move the girls around by using smaller paddocks or other means. I'll often just let them out an hour or two before sundown and herd them into a space where I want them to scratch (keeping them out of new garden beds). As night falls, they quickly make their way back to the coop.
Think about capturing water and
energy. Can you capture water at the top of your property and slowly move it down through the land? How can you capture the most sunlight? You'll want your tallest trees away from the direction of the sun, so that they don't shade-out everything else in the food forest. If you are going to take a few years to develop your property, experiment with cover crops, particularly in your winter season. Find a cool season cover crop mix (multi-species) and sew it over the winter. This will not only protect the soil from hard rains, it will build soil fertility, and it will show you where you have the best soil already. Capture all that sunlight, even in the winter.
One of the last things you do is actually plant your trees, shrubs and gardens. It is frustrating to have to wait to get the trees in the ground, but I've learned again and again to really think through placement because once a tree is in the ground, it's very difficult to go back later and move it.
Make sure you give your little trees adequate space to grow into big trees. A common mistake people make is sticking a little into the ground too close to other trees—they look so lonely standing out there in the middle of all that space by themself. In 5 years, they are crowding each other and you are constantly having to prune them to maintain any sunlight down through to the soil below for other plants. Too much space is much better than too little.
Fruit trees need room for air to move through them——give them at least 3 or 4 meters between them.
I would agree with the poster's above who caution you about eucalyptus. There are so many better trees that will add multiple functions to your food forest than eucalyptus without any drawbacks. I live in a similar climate as yours (although not as much rain as you get) and I've seen what nasty eucalyptus trees do to the soil around them. They basically sterilize the area beneath them so little else grows, they don't fix nitrogen, they don't attract
bees, and the wood isn't very good for tools or lumber. Please consider other options. Even just planting moringa for the first couple of years would be better than eucalyptus.
Best of luck. You may wish to search through this forum for this same topic—it seems to get asked
alot ("I just bought my land -- what should I do first?").