When I worked in Sardinia in the 80s, the festivals on the island were far and away the best in Europe.
I’ve written more on l’ardia di San Costantino, the incredible horse race held in Sedilo, where I lived for four summers.
I’ve also written a brief intro on the archaeological richness of Sardinia.
You can get a Sardinia Map and Distance Calculator on Italy for Visitors.
Sardinia is a fascinating place. Don’t get hung up on the Costa Smeralda. Go to the interior.