How long is a piece of string? There is no set rule when it comes to budgeting your landscaping - creativity is endless but this is about you and what you are comfortable spending and seeing the value in your garden.
Do you need an entertaining space with cooking areas, lounge, focal points as well as lawn, edible garden, decks, pathways, storage and utility areas etc. Do you want some art in your garden?
One thing to remember is that a grand home deserves a grand garden. There is nothing more incomplete and heartbreaking than to have a beautiful architecturally designed home and interior with a garden that does not reflect this.
As a guideline and through studies that have been done, you should invest 10 percent of your home value in landscaping.