Several people have asked me to comment on some of the practical aspects of my June-July 2014 Camino. I must emphasize that these are my opinions only, and that many will disagree. There are many available sources to use to form your own opinion.
Money: from California estimate $1500 or more for a round trip ticket, $300 more for travel in Spain (train, bus, taxi). For a 40 day trip, I would budget $60 a day…. around 40 Euros. This is high, but you will want the occasional hotel and dinner out. That makes $2400 + 1800 = $4200. You may also spend 300-500 on the right pack, shoes, small sleeping bag. Make sure you have a good working credit and debit card. Credit Unions have far lower fees than regular banks for withdrawing cash or using credit cards abroad, so get set up with a credit union. You can of course spend less daily. I often relied on a tomato salad with bread and tuna , fruit on the side, that I made in a hostel kitchen.
Time: I would give it at least 40 days for the whole thing. The Brierley guide is excellent, but if you want to stop to smell the roses, I would walk two days for each of his stages. Choose shorter stages, or choose a portion of the route to walk.
Distance: If you were backpacking in the Sierra, you probably would not walk 15 miles a day. Unless you are sure you can do it, 30 km a day is a long, long way. I saw many people injured and ill from trying to do too much. Also, starting in the Pyranees seems to me to be a point where many people injure themselves or get ill. Go shorter distances, start very very slowly, and WALK AT YOUR OWN PACE. This may not fit the guidebooks. I must emphasize that it is crucial you do everything you can to remain healthy. I saw so many people almost punishing themselves, and harming their bodies, on this trip, pushing on when they should have stopped.
You get a Compostella for walking the last 100 km into Santiago, starting in Sarria. So thousands of people, and schoolchildren, choose this route because it is the easiest way to the document. The path is very crowded and is a very different vibe than other parts of the Camino. That is the rule of the Catholic Church– walk the last one hundred. The Camino is far more than the document. You might consider an alternative route and skip the Compostela. God will understand.