I usually try to travel as light as possible. With that in mind, I try to keep with me a selection of tools that can get me out of minor trouble such as flats and small crashes. I usually don’t prepare for every possible scenario. I feel, that if something goes really wrong technically or I crash big, a wide selection of spanners won’t be enough to rectify the situation.
The things I want to be able to do on the road, i.e. what my toolkit is planned for:
taking of the front wheel and changing the inner tube/tire
14mm hex bit, 10mm socket or wrench, tire irons
taking off the rear wheel and changing the inner tube/tire