I would have liked to have known that I didn't need a thing for every possible trail contingency, like comprehensive repair kits and whatnot. My first backpacking trip way back in the 80s consisted of a massive 50+ lb. load because I had all sorts of stuff I didn't and wouldn't need in my pack. 

As a related thought, it's always great to encourage newcomers by telling them that they don't need any fancy gear or clothing to enjoy the outdoors. In fact, the simpler, the better, at least for starting out. Once they develop some experience, they can make more informed choices about what gear they might need to enhance their adventures.