Whether you plan to "borrow ideas" or plan on making your own landscaping design, you must have at the very least a simple understanding of the values of landscape design. Here's a good read about landscape design, check it out!
Don't feel that you have to put on every principle to every part of your plan. Just having an understanding of these principles can help you produce ideas and increase your resourcefulness.
Great landscaping lies in the eyes of its creator. So, while the principles of landscape design are great procedures to follow, don't feel like they're the "have to rules" of landscaping. Abstract and creativity are permitted.
Unity must be one of your main goals in your design. It may be better agreed and applied as constancy and recurrence. Recurrence creates unity by repeating alike elements like plant groups, plants, or decor during the course of the landscape. Constancy creates unity in the sense that some or all of the different components of the landscape fit together to make a whole. Here's a good post to read about landscape design, check it out!
Unity can be shaped by the constancy of character of elements in the design. By character, I mean the height, size, color schemes, texture etc. of diverse elements.
A good sample would be in the use of accent rocks and boulders. If you've ever seen a landscape design that had numerous different colors and sizes of boulders, then you've seen that unity wasn't shaped by this specific element.
This is just one sample but the principle applies to all other elements such as groups of materials and plants.
A simple way to make unity in your landscape is by producing theme gardens. Producing a theme garden is easier when it's related to something you're interested in or have a desire for.
If you're interested in butterflies for example, you could make a theme using plants that attract butterflies as well as using ornaments, statues and other decor that are connected to butterflies.
Unity must be expressed over at least one element in your landscape and preferably more. Using components to express a main idea through steady style and a precise theme is what makes harmony.
Simplicity is really one of the principles in design and art. It's one of the best guidelines you can follow as a beginner or do it yourself. Just keep things simple to begin with. You can do more later.
Simplicity in planting, for example, would be to pick two or three hues and repeat them all over the landscape or garden.