Hi ,
I have cycled fro Le Puy to SJPD and from Porto up to Santiago. First trip bought two cheap bikes in decathalon, nothing special in them, had no problems sometimes went on camino track othertimes went on small roads off track, biggest problem, if it is wet your gears will clog up on the track then you need to be able to carry out some bike maintenance. Met some serious bike riders with some serious bikes who laughed that we were going to Santiago on "That" bike, had a great cycle if the wheels turn then wheather the bike costs 1000s or 100 euro it will go. Second trip brought my own bike over I cycle a Giant hybrid (See pic on avitar) with Butterfly bars and suspension seat and a granny gear for big hills and have taken it places where serious mountain bikers would look twice. Sometimes you may have to push your bike wheather through mud or up steep hills. Enjoy the adventure, remember all your utterances may not be prayers oon occasion.