Welcome to Spain Ferus!
What is good, depends on what type of food you are interested in. What do you like? We can give you more specific recommendations if you are after something.
quick tip: most restaurants offer a "menu del dia" which is their frix prixe lunch menu consisting of 3 courses, allowing you to enjoy sometimes the most expensive restaurants for cheap. Menus are almost never 15 euros, and you get a lot of value.
here are some suggestions. I'm big on VALUE.
Best for Spanish Tapas:
Vinitus
https://goo.gl/maps/FG6BoAD2woP2
- run by the same people as Cuidad Condal, this is their more upscale-feeling tapas restaurant, yet it feels like the prices are CHEAPER because of the value you get. You can get tapas as good as this in a lot of other places, but you pay more, and sit in cramped spaces with a whole bunch of tourists. As long as you come near the start of meal time, you'll always get a comfortable seat to enjoy the amazing food
Best for Breakfast anytime:
Brunch and Cake
https://goo.gl/maps/r7CN2tP1cg52
- you see crowds, not just lineups, for this restaurant during peak times because they dont take reservations. If you are looking for American style breakfast, but a lot classier (and cheaper than Denny's), this is it.
Best for Dinner:
Etapes
https://goo.gl/maps/3SEL7ezA2xr
- it's in the michelin guide as a top restaurant to visit, and honestly, could get a michelin star, but I hope they never do because that would no longer make this restaurant so accessible. Imagine a michelin star restaurant's set menu, but double the portions, and only 35 euros, and you will get Etapes. You will feel full and satisfied, eating slow cooked lamb, tuna tataki, duck, and homemade tiramisu.
Best for Drinks:
Paradiso
https://goo.gl/maps/TxR6jGdziFU2
- on the outside, it's a pastrami shop, but ask to go through the hidden door, and you'll be taken into a cool speakeasy, making some of the tastiest cocktails in barcelona. How about a caribbean-inspired cocktail served in a seashell, presented in a treasure chest with fog and mist flowing off the edges? How about all that for around 10 euros? If you want to impress someone too, take them here
Best Steak/Menu Del Dia:
Buenos Aires
https://goo.gl/maps/unhjBS5p4aH2
- big huge argentinian steak, scallop salad, coffee, and cheesecake, all for 13 euros, AND everything tastes amazing. You can't cook the same stuff at home for 13 euros. There's a reason why this is one of the top restaurants in barcelona according to tripadvisor
Lots of other recommendations depending on the type of food you like, so just ask in this thread and we can give you something more specific