I mostly use a poncho but they can be a nuisance in strong winds so I always carry a rain jacket (and trousers as well). I get my ponchos from the sort of shops in spain that sell farming goods. They cast about 20 euros and seem to be favoured by the people who work on the land.
You most definitely do not need them. However, you may want to use them.
On all of my caminos I have always just carried a single pole (normally strapped to my back pack) for those tricky water crossings and to fend off the odd overly intrusive dog.
It does seem to be the case. I have walked a few caminos and often walk 40km or more a day and very rarely get any blisters at all. It seems my feet are a ‘standard’ size!
Given that water is the most important item to have with you then I take 1.5 litres in a bladder (I find having the bladder with a drinking tube means I drink more frequently) and carry another 1.5 litres as a spare.
I just use inexpensive no branded tee shirts made from Polyester. Quick dry and easy to wash. They do the task well and never seen the need for anything else.
Never found any DWR that works for my golf shoes so never bothered for my walking shoes. I never worry about my feet getting wet, they dry out soon enough and even on the occasionally very wet days (rain and rivers) it has not been an issue.
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