Hi, welcome to the forum.
I suggest that you search through past threads for more info. There will be A LOT about footwear. It's one of the top 2 or 3 topics of debate here. Top 3 seem to be: footwear, walking poles, phone cameras. Re footwear, there are 2 sets of preferences: Structured boots or trainers. There are many other topics covered in this forum, of course, but the most contentious ones are those 3, it seems to me.
There was a very interesting discussion recently about blisters. That's a complex issue which it seems is not necessarily solved by choice of footwear.
The essential factor is: Everyone is different. Blisters: Skin layers can be prone to shearing in one person and not in another. Then moisture and friction become the major contributing but secondary factors. Footwear: some people want comfort and don't mind occasionally wet feet - go with trainers, they are more likely to get wet but dry quickly; boots are heavier, stiffer, more likely to be worn by people (like me) who try to keep their feet dry and need ankle support. I have no opinion about sandals.
I suggest that you train for as long as you've got before you leave. Long distance walking is an unusual experience for any body and the various stresses effect everyone differently. With luck, you will learn about any specific weaknesses before you're out there and don't want to quit.
A lot of people, but certainly not everyone, develop plantar fasciitis. The relatively sudden onslaught of a huge amount of exercise can bring on a bout of plantar fasciitis. It can be agonising. I suggest that you be wary of mainly the macho, older guy who's mantra is "Just go for it".
I don't know how far you're planning on walking, but I strongly suggest you don't dive into a very long walk as your first Camino. Try 200kms or 400kms, it's not a competition, enjoy yourself.
Walking poles take some weight and stress off muscles and joints (some say 10% or more!). I've only walked The
Camino Frances but I can tell you that there are quite a few descents there which can be very strenuous due to very uneven surfaces, and which are dangerous when wet or muddy.
It's not true that modern boots need breaking in. An all-leather boot will, but almost all modern boots are made mostly of fabrics and synthetics which are pretty much ready to go. I have a good pair of Scarpas. They fit perfectly, I chose socks very carefully, I've never had blisters. But that's me. The climate while you walk will be a big factor - heat changes all variables. I walked in early spring, it was cool but manageable and I found it great weather for walking. By ready for wet weather, water can run down your legs into even waterproof boots.
You're going to get a LOT of answers about this. This topic comes around often.
Good luck and Buen Camino, - Mike