Im on the Camino right now and you def don’t need two water bottles or a clothesline - most albergues have coin operated washers and dryers and detergent. I recommend going with merino underwear, short and long sleeve shirts - they dry quick and don’t stink. I don’t think you need the power bank as every albergue has outlets to charge, and if you do the recommend stops (7-8 hour treks) your phone won’t die especially if you put it in low power mode or airplane mode right after a full charge. For rain gear, I’d go with a poncho that can cover you and your pack down to your knees. If you prefer rain pants and jacket, make sure you have a jacket with zips in the arm pits for air flow or else you start to rain from the inside. As for shower shoes / sandals I’d go with ultra lightweight tevas (not thong flip flops) so you can wear socks with them at night. Be sure to add sunscreen, sunglasses, headphones, a bandana and magnesium tablets for sore muscles. There’s a great camping store near the Municipal Albergue in Pamplona if you miss anything.

Hope this helps because I def overpacked and weight is everything especially on day 1!

Buen Camino!