Annuals versus Perennials ...oh, which one is better?
Annuals are so great because either you can just go out and buy some and you have instant color for almost the rest of the growing season if you care for them correctly. You do want to think a bit about how the colors complement or contrast with each other. Also how the heights vary from the front to the back of your garden beds so you do not hide the shorter plants. The height and colors you have work through with your perennials too.
Perennials need to have planning involved so that the timing of their blooming periods overlap yet follow one another to achieve some color in your garden throughout the growing season. You have to realize that there will be areas of just green spaces where some perennials will either be coming into bloom or going dormant. To offset all the green, you can take into effect the foliage of your perennials. This means pick some gray greens like silver mound, chartreuse, or a variegated type, or you could pick different leaf styles like a finely cut fern leaf, a heavy waxy sedum leaf, a wooly lamb's ear leaf, or spiky type yucca spears and so on.
Money-wise annuals are cheaper for one year, but over the long haul you will be shelling out money each year, so that cost will mount up. Perennials will cost more at the beginning, but after you are all set, you will only have to care for them and enjoy the view.
I think that there is a bit of a compromise and use the best of both worlds. Put in as many as you can afford with the perennials, then fill in where you need color with the annuals.
Do what works well for you. Most of all enjoy your garden because that is what is important.