When I prepared for my 1000km walking journey, I read all the lists. I shopped as others instructed, mostly. I stubbornly clung to a pair of cotton pants and a hoody that made me feel comfortable. After a few weeks, I let them go. They just didn't dry fast enough. Generally, you'll be washing your clothes by hand every day or two and air drying them on a clothes line. If your stuff isn't dry, you'll have to carry it damp, or worse, wear it wet.
As I walked north from Seville to Santiago in Spain, I cast off my favorite cotton trousers and a pair of cotton shorts. I replaced them with man-made fibers that were lighter weight and dried quickly. That's the key to carrying everything you'll use for the many weeks of walking on your Camino: light weight/dries quickly. Think of it as your shopping mantra.
The other major issue is keeping your pack as light as possible. Many of the suggestions I found online recommended 20 pounds (or lighter). Lean toward the lighter, much lighter. You'll be carrying water and a bit of food in addition to your clothes, toiletries, and first aid supplies. I'm shooting for 10 pounds before water and food on my next Camino. Because I realized, I wasn't on a 1000km trek, but rather a series of day trips that added up to 1000km.
The time of year you walk also makes a difference. One advantage to walking in the late spring or summer is that your required wardrobe can be as light weight as possible. Stay as lean and light as you can. This is a man's list; women will have to adjust accordingly. Here's how I'll pack next time:
2 pairs of trousers
2 shirts (I like pockets)
2 T-shirts (runner's shirts, not cotton)
2 pair of hiking socks (Smart Wool)
2 pair of underwear
1 light fleece (Moreno wool is always a good choice)
1 light jacket
Bag (Eagle Creek is the lightest I could find)
Bar soap (x2)
4 oz toothpaste
4 razor blades
Eagle Creek Bag
Tylenol 400mg (buy in Spain)
Passport (both travel document and pilgrim's passport)
Credit Card, ATM Card, Cash
Water bottle(s) or Platypus
Trekking poles (optional)
Concentrated Laundry Detergent
Swiss Army Knife (fork/knife combo)
Of course, all of this travels in your backpack. I had a 50 liter pack the first time. Next Camino, I'm shooting for around 38 liters. Lean and light.