Costa Brava is a large region and the practical things to keep in mind will depend on where you are planning to visit, and how long you are planning to stay in the region.
Getting around
The hinterland of Girona province and the Costa Brava coastal areas, have relatively poor public transport connections compared to the rest of Spain.
Only Girona and Figueres are well connected to Barcelona by fast trains. Both these towns feature as popular day trip destinations from Barcelona.
Driving your own rental car is really the best way to get around Costa Brava. However within Girona city , you do not need a car.
Girona and Costa brava have become popular biking destinations. You can explore the region on a bike following well-defined routes.
Girona is not just the gateway to Costa Brava but a popular tourist destination in its own right. Allocate at least a day in Girona.
Best time to visit
Again, the best time to visit Costa Brava depends on your interest. If you are looking for sun, sand, and water, then winter is certainly not a good time to visit. But the winter has its own charm if you are mainly interested in seeing the small towns and experiencing their culture.
Summer is easily the best time to visit Girona and Costa Brava. If you are visiting in the months of July and August, avoid all the popular resorts as they are swarmed with tourists.
Tourist Cards
There is no one tourist card that works for Girona & Costa Brava region, as it is made up of so many individual towns. For your Girona city visit you should consider picking up an M5 card that gives you highly discounted entry to 5 museums of Girona.