I have a sacrificial wallet that I bought for $1 that I keep in my front hip pocket. I put a very small amount of Euros in it and then pad it out a bit with old, single use debit cards (already used up) and other people's business cards. I use this for small purchases (coffee, beer and strawberries) and top it up out of sight.
I have a couple of "travel" debit cards that I use to get cash from ATMs that I keep a float of around €200 in and top up using Internet banking on my phone, as needed. I carry between €100-€200 in small bills on me and choose the amount of top up from the ATM to ensure I get mostly small bills.
I take a photo of my passports, travel insurance policy number/contacts, flight tickets and major credit card and leave that in NZ with my computer literate son. I print a copy for my wife.
I have two passports so I always keep those separate (although this once resulted in a Swiss Immigration Officer quickly pointing his machine gun at me). I distribute various items in various places. I have access to the photos that I leave for my son over the Internet.
My two most closely guarded items are my phone (with strong pin code and always locked) and my major credit card. I carry a medium sized USB powerbank with me and recharge that in Alburgues so that my phone is always on me and recharge my phone from the powerbank as I walk.
Humorous (now) aside:
A couple of years ago I attended a conference in Greece then visited a friend in Portugal before returning home. I entered the Schengen zone at Athens airport and presented my UK passport and was waved through without a stamp. Flew from Athens to Oporto after the conference then after visiting my friend presented myself at check-in at Oporto for the flight home and conscious of matching inbound and outbound passports presented my UK passport. Emirates check-in person took some time looking through my passport several times then announced that I could not board the plane!
I realised that they had been looking for my re-entry Visa in my UK passport (which doesn't exist) I reached into my coat pocket, pulled out my NZ passport and gave them that.
The annoyed Emirates check-in person scowled and said that I should have used this passport and that I should use it if asked again on my journey home.
That day I was slightly over weight with my luggage and so I was wearing more clothes than usual, with a large raincoat over everything (the forecast was for rain in NZ) and I have a long beard and slightly olive skin.
I didn't really notice that I didn't go through passport control in Oporto. My flight required a change in Zurich for the leg to Dubai.
I now realise that Zurich was my exit from the Schengen zone and so I had to go through passport control there. I duly presented my NZ passport there to the heavily armed Official. Us Kiwis are not used to officials with guns and so that was disconcerting in itself.
The Swiss officer looked through my NZ passport several times, carefully reading every page. Then looked up and asked me where and when I had entered Europe? I told him Athens and two weeks ago and he re-read my passport several times.
I then clicked (duh) that he had been looking for my entry stamp and so I went to put my hand into my (bulky) raincoat pocket to pull out my UK passport to show him.
Before my hand had moved more than a couple of centimeters he dropped to an attack stance and pointed his machine gun at me with his finger on the trigger (gulp).
The barrel of those guns sure looks huge when they are decimeters away and pointed right at you!
I stopped absolutely still, hand part way to my pocket although I did clench my anus to stop myself from shitting myself
After what seemed like ages but was probably seconds I said "I have dual UK/NZ nationality, in my left coat pocket is my UK passport. I used that to enter Greece. May I take it out and show it to you?"
He considered that for a moment and then still aiming his gun at me, nodded his head. By this time the people in lines around me had all scattered. Then, very slowly, with finger and thumb I reached into my pocket and carefully pulled out my UK passport and presented it to him.
With this he slowly relaxed, took one hand off his gun and opened my passport to the photo page, looked at it and me and then relaxed and put his gun away. This, then, allowed me to relax.
After reading through my passport a couple of times he waved me through and said "Please use this passport in Europe in future".
I now laugh
when I remember this incident but it was somewhat scary at the time.