Hello,
based on my own positive experience, I can only strongly advise planning the garden from the very beginning. Have the planning done by a landscape architect, especially the selection of suitable plants and trees. This way, as much as possible can be taken into account from the start. I would also try to implement as much of the garden as possible immediately, especially planting larger trees and establishing perennial beds. For these, correspondingly large planting pits can be provided right away and not just 10 cm of soil followed by gravel. If you later need larger equipment in the garden, half of the garden will be ruined again, and then you'll rather avoid it. In any case, a beautiful large house also needs proper planting and landscaping of the garden, not just a few stones and thujas, otherwise it looks like it was intended but not done well, as mentioned above. By the way, properly planned and planted perennial beds require very little work, probably even less than lawns. So please don't save on the garden ;-). If you have a proper concept, you don't necessarily need a professional landscaper to implement, for example, the paths, terraces, stairs, edging beds, etc., smaller regular construction companies often do this for significantly less money. However, they cannot provide advice on plants, etc., and need clear specifications.
Have fun and best regards
Oli