My minimum is also my maximum : never patched spare tube, patch kit, tire levers, pump, 4,5,6, allen wrenches, 35 mm film cannister of quarters. All of that in a small saddle bag.
I consider all my rides "training" rides not touring so I'm never more than 50 miles from home or else I might consider more. But thats all I've ever needed, beyond that I'd just call my wife to pick me up and fix any mechanical problem at home.
Btw, I have had more than one flat on a single ride, so that's the reason for the patch kit. I've also used the allen wrenches for saddle and stem adjustments while out riding. I use the quarters for 50 milers for sweet tea and if longer than 50 miles I use the quarters for a coke and peanut butter crackers. As usual ymmv.