I'm with this man though organised slightly differently. I set off dressed for the weather conditions at the start time. Other than a rain jacket I prefer to wear what I need and remove as necessary. In a small under seat bag I carry:
- multi tool
- 10 and 11 speed quick links
- two tubes
- two tyre levers
- patches
- cafe lock
- cleat screws - I have a tendency to lose these!!
- £20
I keep meaning to buy a CO2 cannister but only think about it during a ride and then forget!
In jersey pockets:
- central pocket - pouch style wallet containing phone, credit card, cash, emergency details and medical card
- central pocket - survival blanket. Has been used for other riders. I view this as an absolute essential
- right pocket - cereal bar or current choice of food, Glyceril trinate spray in case of heart issue (I'm a survivor)
- left pocket - Crank brothers tyre lever
- in winter I add a spare base layer very tightly rolled and covered in cling film. Rain jacket if needed
On my wrist I wear a onelifeid band which gives a medic full access to my medical history, contact details, NHS history etc. £15-20 every cyclist should do this in my opinion. Around my neck an orienteering whistle for when I'm laying in a ditch with a broken leg and unable to move.
I utter not a word of criticism of other riders as we all make our own choices. In all my cycling years I have never experienced an issue, nor seen one for a friend, which couldn't be covered by the above. What does go wrong? Punctures and the very, very occasional snapped chain. I see no point in carrying anything else. The unfixable issues I've seen are smashed deraileurs after a crash/falling off, trashed wheels where the side has blown out. These guys had to phone a friend.