Your best low-cost option for long-distance travel in Spain is to take buses with Flixbus. You can download their mobile application on your phone, and their website contains detailed information that will guide you from the first to the last step. The buses are comfortable, with plenty of legroom, and the prices are unbeatable.
Carpooling is also an excellent way to get around Spain. In addition to being environmentally friendly, it will allow you to meet local people. Although carpooling may be limited in some regions, it's still worth checking out the BlaBlaCar website. This carpooling service is safe and frequently used in Western Europe.
Have a great trip and be sure to make the most of your visit to Spain. Don't miss out on the best attractions to see in Barcelona!