fwiw, I've been down a lot of the gadget paths over the years. These days, my bikes are all kitted pretty similar.
* water bottle cages x2 ( locations vary by bike type )
* under seat kit for roadside repairs
- two tubes
- patch kit
- tire spoon x 1
- CO2 cartridge x2 and pump cap
- multi-tool ( variations based upon bike )
- bandaids
- neosporin
- emergency money
- emergency contact info
* lights
- one white forward facing (150-750 lumen depending upon bike usage)
- two red rear facing (300 lumen)
* bluetooth speed and cadence sensor
Commuter only
* fenders to reduce splashing
* rear rack
* water proof pannier bags
* additional rear facing 750 lumen red lamp on rack
* flashlight
* traditional travel pump
* crescent wrench
* bike lube
* spoke wrench
Items that are not one the bike, but are always on my person
* road id
* wallet
* sunglasses
* cellphone (in waterproof pouch either armsnrap or jersey pocket)
* tomtom multisports watch (paired to the bluetooth devices) - may switch to Apple Watch
Notice, no dedicated bike computers, no dynamo/generators, and I don't want the phone or watch in a place where I look at them. Why? fewer distractions while riding. Several items carry on my commuter are not for me, but are for use in assisting other cyclists that I encounter with mechanical issues and no tools or ability to deal with them.
While there remain lots of interesting gadgets out there, none of them are effective at enhancing the ride experience, so for the most part I quit bothering.