This is the Spanish part of a 1 interrail trip. Since the destinations before dont really make sense if a personal connection to the places is missing, this is the itinerary of Spain, which is possible to travel if you are flying to Barcelona or entering from France by train. We travelled as a group of 4 friends in their early 20's, trying to spend as little money as possible.
Although the whole trip took us 11 days, make sure to spend more time at the places if you are able to do so!!!
Since we owned an Interrail Ticket, we travelled to every place by fast train, which is very convenient in Spain. However keep in mind that in Spain seat reservations on those trains are mandatory, meaning that you have to pay extra for those (between 4 and 10 Euro per ticket) and more importantly, have to make those reservations in person at the trainstaition or one of the offices.
We stayed at HelloBCN Hostel. Which was a cheap option for Barcelona and offered everything needed as well as a quite nice atomosphere. However we always booked accomondation rather spontaneous, meaning that the best pick wasnt always available, and this was definetly one of those times.
When it comes to Food, Barcelona is rather expensive. I would reccomend trying to stay as cheap as possible (if you are on a thight budget) and start to dive into spanish cuisine in the south, where eating out will be much cheaper and just as delicius. (I am talking about 8 Euro per Tappa vs 2 Euro per Tappa).
Of course the Park Güell and Sagrada Família are must sees, and should not be missed even if you pay more than ususally. (Make sure to get tickets online for the Sagrada Familia when you are planning your trip, there are limited visitor numbers.) Something i can reccomend was a "Free-walking-tour" through the Gothic quater. (Pay as much as the tour was worth to you afterwards.) There is a little hill you can climb (or take the "Transbordador Aeri del Port" , a cable car) which offers you nice views. A trip to the beach is also quite relaxing if you are into that, and Barcelona offers amazing Night-Life
Barcelona is a city with endless possibilities and you will find activities that will match your personal taste without any problems!
Advice: look out for pickpocketing, especially when going out