On my road bike:
- spare TPU tube
- TPU patch kit
- minimal multi tool
- tyre levers
- quick link
- a few zip ties
- small abus wire lock (combiflex)
- 20€
- a few small odds and ends
+ a mini pump mounted to my frame and a small electric pump in my jersey pocket
It sounds a lot, but it all fits in a small saddle bag.
On my gravel bike I have all of the above plus:
- tyre boots (saved my arse once)
- latex gloves
- a pocket sized torque wrench
- spare battery for power meter and speed sensor
Maybe a bit over the top, but it still fits in a medium sized saddle bag.