In my most humble opinion (snort), I feel it important that each and every person have some basic knowledge of plants. Now it could be just because I happen to LOVE plants...after all, they "make" the air I breath, fed my belly, and sooth my soul with their beauty.
All over this earth, since man has been here, he/she has used plants to survive and thrive.
And yes I know how "many" opinions there are out there.... everyone has one. And that is great since it allows us to have an exchange of ideas and thoughts. Then each of us can glean out of this immense and vast pot of knowledge for those things WE feel are important for us and our family.
My suggestion: do a inventory of what your family NEEDS. Are there health problems? If so, what is used for the care of these? How much do you use? How hard would it be to GET these if society fell apart? Now think about and do some deep research on what plants these things FIRST came from. Most pharmaceuticals are around because plants were used first. Plants were the guides. Not all, but most.
Now learn all you can about those plants. Where do they grow? Can YOU grow them? How would you use them? Exactly how would you PREPARE them? In other words, get to know them. Intimately. Do try to grow them or see if you can find them in nature.... or find them in nature first and when they make seed, snag a few and then try to grow some. (Use care for any endangered species, huge fines can be placed if laws are broken....this should be part of your research)
If you have time and patience, learn how animals use it....what pollinates it? what scatters its seed?
Now if you do decide to try it, go slow....only a little. You can see if may be allergic by rubbing a bit on the inside of your arm.... a LITTLE! Use some common sense. Pay ATTENTION to any WARNINGS you came across in your research. Talk to people who have used it. There are some great groups on the internet that can give you their experiences. But don't expect YOURS to be exactly the same. We are unique individuals after all.
Once you get to really KNOW one plant...move on to another plant.
I HIGHLY suggest you keep some sort of notebook, where you record everything you learn about the plants you research....and I mean everything. From online research to the day you plant a seed (or transplant a plant) to all the end results. It can be in some sort of online notebook but I suggest you go "old school" and keep it all recorded in good old pencil and paper. (pencil will not 'run' like ink does if it gets wet, btw) Do both online and hard copy!
Then PASS YOUR KNOWLEDGE ON! Leave a wonderful "library" for your offspring. Share with others in those groups you learned from. Start a facebook (or other) page and talk about wonderful plants! Even if you do not feel comfortable posting actual "advise" about plants, and don't feel bad, many of us feel the same way.... encourage others to get to KNOW plants.
This does not mean you have learn all hundreds of thousands of plants in the world.... just start by getting to know ONE that will benefit YOU or your loved ones.
Have a great day!