A great garden doesn't require gallons of water every week, just skillful planning and a couple years to let plants settle into their places.
Here are the steps:
1) Know your garden, the soil texture, the rainfall in winter and summer, the lowest temperatures you can expect.
2) Know yourself. How much work are you willing to put into soil preparation? How much watering do you want to do in summer - none, a couple times or every two weeks?
3) Make a list of the plants that fit your desires and the garden's profile. If you have heavy soil and you'd rather not add perlite or gravel to lighten it, cross off the most drought-tolerant plants. These usually require a light, air-filled soil, especially in the Northwest. But you still have plenty to choose from.
4) Now plan your garden, the curves, the harmony of lines and paths. Decide where the plants on your list would look best.
5) Decide on the best places for a "holding area," somewhere easy to water that small, newly acquired plants can spend the summer before being moved to permanent positions in fall. Selection is best in spring but planting for drought-tolerance is best in fall.
6) Now divide your planned garden into sections that can be filled with plants all in one year. Why? Because a garden bed develops drought-tolerance as a whole. If you plant piece-meal, you'll always being starting over with regular watering in that spot, hauling the hose over more frequently than the other plants need.
7) Now, finally you can start buying plants! Definitely the best part of gardening.