One kit that I think is undervalued in the bigger picture is a sewing kit. Often, folks (myself included) are quick to seek out what's new and purchase new gear rather than breathe new life into an old piece of gear.
With practice and patience, I've had a lot of personal success repairing, improving, and creating gear that I use daily and others that I carry with me when hiking and camping. I did all of this with just a needle and thread and a high level understanding of how to sew (I am certainly not highly skilled but I can get functional results).
Here is an overview video of the simple tools I use and what I have accomplished with them:
I picked up this pack from mountain girl on a great deal. It had a couple of holes in it but nothing that was beyond repair. After spending a few dollars at a craft store, I was able to fix up the pack and restore it's original functionality.
And here is a close up of the dump pouch I made.
Thanks for looking and let me know if you have a similar philosophy.