I don't know which is worse, starting with a worn out garden or beginning with nothing at all. I have done both, and I think the most difficult is rejuvenating an old garden - what to keep, what to discard is the continual question. Most likely one is stuck with established shade trees (unless expense is not a problem) and huge evergreens, shrubs and low growing evergreens being easier to take out.
I will use my daughter's home as an example of long past their prime plantings. Slowly, as her funds allow, I do a plan for each area, replanting the gardens with plants that are easier to maintain and have great eye appeal.
In the large perennial garden bed, we removed just about everything except some daylilies and the Sweet Autumn Clematis along the back fence (now being cut to the ground each year - see how large it gets with yearly cutting). The garden has just begun and constantly changes, many types of daylilies and phlox, pink and red double knockouts, shasta daisies, gaillardia, rozanne geranium, may night salvia, russian sage, and autumn joy sedum. The four rose bushes are the backbone of this garden and are blooming until the snow flies. In the spring is is filled with hundreds of daffodils of many varieties - hardest part waiting for the tops to die down without pulling them or cutting them down.
Along her front porch and the front of the home were fifty year old yews that have been removed and replaced with Endless Summer Hydrangeas and Chicagoland Boxwoods, a new magnolia, Blue Dart Myrtle groundcover, Blushing Bride Hydrangeas, hostas, ferns and some saved astilbes that were on another part of the property. Most of the plants were found at Home Depot at very reasonable prices
A large area along the side of the home has just been cleared of pachysandra, tree roots and overgrown shrubs. I have done a plan for this area which will take awhile to complete because of the expense. All that is there now are some new Green Velvet Boxwoods and a Limelight Hydrangea (they may be moved eventually). I am going to really have to rack my brain to come up with a cover for those heating exhaust pipes! Plantings have to be four feet away - any ideas?
At my stage, I want everything to be instant but a little bit done each year with planning and using the correct plant materials, becomes a very satisfying accomplishment.