Choose a connected base
Start with Cagliari, Alghero or Olbia rather than trying to cover the whole island. Each has airport links, walkable neighbourhoods and a useful mix of local buses, tours and transfers.
For a first trip, two bases are usually enough. Moving every night looks efficient on a map but spends too much of the trip waiting for connections.
Make the coast a day trip
The most remote coves are easiest by car or boat, so use scheduled boat days or a small-group excursion instead of trying to recreate a driving itinerary by bus.
Confirm the last return service before leaving your base. Sardinian public transport is often excellent for planned journeys and less forgiving for improvised late returns.
Keep the route realistic
A seven-night no-car trip can combine Cagliari and Alghero, or Cagliari and Olbia. Treat the long cross-island transfer as a travel day, not a sightseeing day.
Book airport transfers and intercity legs before peak summer dates. Keep a little space in the plan for weather changes, especially for sea trips.