I'm going to do el Camino del Norte one of these days. There are a ton of guides and information online. I think my friend who did it told me to budget 30 Euro a day...many times less, a few times more.
About lodging, many of the albergues don't take reservations and it is first come first serve. A good guide will have all this information for you and will divide it into the etapas. I've been to many of the cities, and they are all amazing in their own way.