I'm always going to recommend poles. I started the
Camino Frances without them and had I not bought them I don't think I would have finished. I'm also about to start the CP from Porto and my ticket is "carry on only" so I will be buying poles in Porto. But some people get on fine without them and rumour has it that the CP isn't as demanding as the CF.
DSLR camera - this one is on you. I'm just bringing my phone, but the quality of the camera was a determining factor in my phone selection. I understand it is not the same as a DSLR, though.
Camelback or not - when we walked on the CF my son had a camelback and I had a water bottle in the side pocket of my backpack (two on days with a long distance between fountains). He liked bring able to sip water whenever he wanted, even while walking with his poles. I liked being able to easily refill and not have to start the day with the weight of 2 or 3 litres of water. For this Camino I am taking a drinking tube that attaches to any water bottle. The best of both worlds.
Rain jacket or poncho - last Camino I took a super-lightweight rain jacket and never used it once from Roncesvalles to Finisterre. So, in retrospect, I'm glad I prioritized the lightweight. This Camino, I don't expect that kind of luck. I've heard since praise of the simple, cheap ponchos from IKEA and got one of those as well. I will bring both. On cold wet days I will wear both. On hot wet days, just the poncho. With a short sleeved shirt I won't worry about my arms getting wet. On cold dry days I will wear just the rain jacket over a hoodie as a windbreaker. A final note on this: if you are wearing a poncho you probably want a hydration system of some sort with a tube that you can access with the poncho on.
- Umbrellas are great in the rain unless there is a wind. And if you are taking poles, you want one that you don't have to carry in your hands. I won't be taking one. But if I were to walk the CF again in July/August, a reflective umbrella that I could attach to my backpack would be well worth it to protect me from the sun.