How do I make over the landscaping of my plants?

Make a list of all the plants you will have and any decor items. Then group them together based on your desired outcome. Example: Do you want like items or a variety of color? Do you want them to stagger blooming so that something is in bloom all year? Do you want filler? Check your sun exposure and watering requirements. Then make a plan and start moving things around. You might not have to move as much as you think.

Short things in front - taller things in back. Sometimes more pleasing in groups of 3.

Kathy is right but you also want to consider which plants require the same of close growing conditions and fertilizer. Some like acid (roses, azaleas etc.) and others don't. When you try to grow these different plants together they don't do well. Also, are your gardens against a wall or the house? Usually you put the taller plants against the wall/house and get smaller as you move outwards. If your planting in the open the taller plants are in the center and you work smaller as you go out. I like to mix up the colors as well as make sure I have something in bloom all growing season so I mix and match. I used red bayberry as the vocal point in one then planted lower marigolds in two different heights and finally lower plants around the edge in different colors. I like it alot.

Various heights and select plants that bloom at different times of the year. I also like to add in some 'annuals' and pots.

Or . . . Bite the bullet and hire a landscape designer or architect.