My best investment was a book called Poverty Prepping, How to Stock up for Tomorrow When You Can’t Eat Today. by Susan Gregersen it cost 2.99 on Kindle. I gave or recommended it to all the kids and several relatives who thought they couldn’t afford to prep or didn’t know how to get started. Kind of a prepping starter which helped them to start thinking differently and in the right direction. It helped get more relatives on board.
The second one cost more at 99 bucks and was a sun oven which could feed the whole family, not one of those back packer specials for one. So that was a no fuel needed except the sun and even works somewhat on cloudy days (for warming things) a nice safety issue since there is no smoke for unwanted visitors to zero in on and using a plastic bag and turkey roaster no smell til you open it.
Of course those were purchased, the very best Items cost nothing and were given freely on forums like this by people willing to help others with their own knowledge and experiences over the years. Thanks.