After being a tourist in Spain then returning to live there for over a year, I got to know the country quite well with what's great to see and explore but also what is great to eat!
On average when I went out to a restaurant with friends, I would spend between 6 - 12 euros depending on how many Tapas we bought. Tapas are basically a bunch of appetizer plates that you would share during the meal. Sometimes you don't even have a main dish, you just eat lots and lots of Tapas and don't worry you won't go home hungry.
Here is my list of foods & dishes to try & enjoy in Spain.
Jamon. Spanish Ham is a staple in everyone's household. It's very popular because of they way it is cooked. It is dried out for about a year before even being served.
Tortilla de Patatas. Spanish Omelet. It's simply potatoes, eggs, and salt. You can add other ingredients like I did with my homemade tortilla below. I put some onions and sausage in it!
Caqui. This is a very popular fruit that is grown in the south of Spain. I had it almost after every lunch.
Patatas con Lemon y Sal. This is a very traditional way of eating potato chips in the region where I lived in Spain called Murcia. In the South they like to put lots of freshly squeezed lemons and some salt and pepper on their potato chips. I loved having this as a snack with my Spanish roommates.
Croquetas. These can be mixed with almost anything and you can put almost anything in them. I prefer my croquetas with mushroom and spinach!
Pan con Aceite de Olivas. The Spanish LOVE to have toasted fresh bread drizzled in olive for their breakfast. I had this almost everyday. I also liked to grate fresh tomato and put that on my bread as well which is also common.
Smooy/llaollao. You can never go wrong after tapas having a tasty frozen yogourt. These two brands were mine and my friends absolute favourite! 
Soup with Albondigas. I like to call this a "Glorified Meatball". It's like a meatball but has lots of flavourful spices compared to the meatballs you just put on your spaghetti.
Cherries. I never experienced picking cherries off a cherrie tree before. My friend in the Valencian province invited me to come to his orchard and pick lots and lots of cherries!
Paella. This dish is what Spain is mostly known for. My favourite paella is Paella de Valencia. It has a mix of rabbit and chicken with a few vegetables.
