I walked le Puy to Condom 5 years ago...booking in advance was a must...get a copy of Miam Miam Dodo...
I started from Le Puy-en-Velay early April 2016, paused at Estella / Lizarra early May 2016. I returned there early in October 2017 and arrived at Compostela later the same month.
I booked ahead only twice.
I made my first booking on arrival at Lauzerte. This was for two nights at Moissac (for La Petite Lumiere) - my first rest day after about 10 days.
At Larressingle, after hearing chatter overnight, I was a bit anxious and asked my hostess in the morning to ring and book a bed at Manciet for that night.
As it happened, I had a minor medical misadventure and stopped at Eauze for two night - Marie-France of La Petite Grange is mine hostess.
After two nights, Marie-France drives me to Manciet to provide a second day of relief for my right anterior ankle joint and to meet my host, two days late. And of course there was room for me.
The method I chose (except when booking ahead) was to enquire at the first gite-d'etape on entering the town and, if complet, to continue through the town until I had a bed for the night.
In April 2016 I always found a bed at the first gite-d'etape, although once it was a close run thing.
And no worries from Roncevalles across to Compostela.
...
In July 2010 I had walked from Sarria and noticed one albergue at Ponte medieval de Ribadiso, just before Arzua.
In October 2017 I noticed not only the original albergue but two pensión that had sprung up alongside.
Of course that was 2016. Some eight years later ...
Kia kaha (take care, be strong)