Good for you!
That sounds a bit snarkier than I meant it to be, but it's genuine praise. My interests in nature, history, and prepping all developed separately throughout childhood and adolescence, and only in the past few years have they converged with my discovery of bushcraft and rewilding. The primitivist community is the only community I've ever felt welcome in, and I hope you feel welcome here as well. PaleoPlanet is pretty good too.
Even so, I've noticed a dissonance between the common primitivist and survivalist mindsets. The ways of the average survivalist are often unsustainable, rooted in modern brainwashing, and ultimately just as dangerous as globalist society or any disasters they seek to evade. Most premade survival kits are marketed by wealthy fear-mongering corporations and contain such toxins and plastic and antibiotics. Good luck surviving the plague without your gut flora.
Primitive ways are largely sustainable, promote fitness and healthy eating, and will ultimately result in a healthier population too far and few to spread pathogens or congenital disorders. There will always be sickness and death. but viruses and mutations would be restricted to tribes in close contact. I'm not worried about pathogens though. Illness can be treated, but our biggest threat comes from the resulting "quarantines" and "evacuations" mandated by the state. Get a shot of mercury and formaldehyde or get a shot of lead.
Both rewilders and preppers overlook the threat of martial law. Some survivalists acknowledge the danger of a pre-apocalypse police state, but they take it too far and go killing innocent cops; most think the National Guard and militarized police are here to help though. Rewilders, on the other hand, rarely seem to discuss the police or military at all. When they do, it's usually in regards to property law and such. Most agree that some collapse is inevitable, this planet can't sustain such a large human population, and so many humans can't sustain themselves against their territorial instinct. Few primitivists mention the greatest danger of such a collapse: the violent response of the government in its death throes.
A balance between the old ways and new ways is necessary at this point in time, as the tumble down from new to old is gaining more momentum with each year. I'd say the most important things you can't buy are the skills to use your gear, but I think you already know that. So I'll just cut to the chase, list my supplies, and explain why if necessary.
*Backpack- Leather or natural canvas (not plastic like nylon or vinyl) in earth-tones. The color depends on where you live of course, but tans and browns are your best bet. Most natural materials are conveniently the right color for their environment. None of that neon orange they market for "safety". Carry no more that 25% of your body weight on your back, as low as 5% depending on age and health, but I'd go for somewhere in the middle. Most of my gear is on thigh/hip pouches, my backpack has mostly....
*Cookware- A small steel or iron (no teflon) Dutch oven, with a couple little serving-size pots and pans, but you can always make your own earthenware vessels with the time, skills, and resources. I have "modern" metal cookware because I expect to be on the move a lot within the next few years. Pottery is heavier to carry and takes some time to make. Shells are also an option.
*Clothes- A very subjective topic. What you'll need depends on who you are and where you are. I live in the midwest, so I gotta have everything from 110 degree summers to single-digit winters covered. A lot of leather and canvas again. Leather boots and gloves, canvas coat and convertible cargo pants, just cut off at the knee for summer with holes to lace the legs back together in winter. T-shirt is just olive cotton
*Shelter/Bedding- At the very least, a blanket and canvas tarp. Shelter is easy to find or build, so it makes little sense to carry the weight of a tent on your back if you're nomadic. Unless someone is carrying it for you.
*Large Steel Bottle- For water, obviously. I like steel because it's light, rugged, and heatable to damn well past boiling if I so choose, but there are other materials to choose from.
That's it for the backpack; mine is large and mostly empty, plenty of room for extra water and foraged food. And useless modern sentimental relics of my mother who died when I was a baby. Like I said above, most of my gear is on hip/thigh pouches. Most weight around the hips, lighter things further down the thighs. So about those things.
*Medical Kit- You want this on a hip or thigh, not buried in a backpack when you need it. Never buy a premade first aid kit. Disregard what doctors and pharmacists tell you, they get bonuses for recommending certain drugs and want to keep you sick so they don't lose a customer. Just like drug dealers on the corner, the money is in the return. Invest time in building your own medical skills. Study biology, anatomy, chemistry, herbalism, field surgery, etc. Don't try digging a bullet out if you don't even know how to suture.
-Herbs: Kept in little tins for now. I almost don't even wanna get into this because I don't know you or what your body needs. You could have a deadly allergy to something I recommend, or think you know enough to identify a plant and eat a deadly poison on accident. Garlic and cannabis are both herbs I recommend with a clear conscience. Allergies are rare and both have so many medicinal uses I don't even know where to start. Garlic and onion species grow wild throughout the world; cannabis on the other hand is illegal and subtropical, but still fairly easy to acquire. I don't recommend cannabis oil because of the toxic solvents used to make it.
OBLIGATORY DISCLAIMER: Some herbs can kill you. Nightshade, poison hemlock, and amanita mushrooms are some of the big names, but there are others out there. Always be 100% sure you know what you're looking for. Safe plants can be deadly if you have an allergy, and even some poisonous plants have anesthetic or other uses in small doses, so always know your body and mind. More than anyone else does. Because while some plants may be deadly, the active principles in those plants are often easily purged by the body in sub-lethal doses; even the "mildest" manmade drugs accumulate in the body and cause massive damage over time. Just do your damn research.
So back to the first aid kit.
-Other Medicine: For me, this means honey, vinegar, activated charcoal, bentonite clay, sea salt, and grain alcohol. All have a variety of uses, charcoal and clay being especially good for poisons, including snakebite. Again, please do your own research before trying to treat snakebite on your own. I've been studying these things for a decade and I'm just not about to trust my life to someone else.
-Dressings: This includes gauze, adhesive bandages, and possibly suture thread if you know how to use it. I'm having a hard time buying those things without plastic (even "natural" band-aids have synthetic adhesives) so I'll probably have to make my own. I've also used pine resin to seal wounds the way some use superglue, so there's an idea. The resin has natural antiseptic properties and less carcinogens.
-Surgical Tools: Most of these I don't recommend unless you know what you're doing and have been studying this shit since you were 11. I've performed "minor" procedures on myself, not something the average modern human can even stomach believing I did. Few ailments actually require surgery, and most of those are the result of acute trauma; internal bleeding and bullet wounds spring to mind. All I suggest is a pair of medical tweezers (technically a kind of forceps) and perhaps suture needles. Nothing sharper unless you have the skill to use it. And all stainless steel.
DISCLAIMER 2: Practicing medicine without a license, no matter how many decades you've been studying it, is illegal. Even when practiced on yourself. A good rule to prevent medical malpractice by the unskilled, but I'm sure it has more to do with preventing true healing by skilled herbalists; a licensed naturopath must still follow much of the dogma of conventional medicine.
As for my other gear, I really have more than I need. The survivalists suggest paracord, duct tape, aluminum foil, etc, but I'm in the process of culling my supplies as well. Strong natural cordage, some pitch, oil/wax, and a few other undecideds on one hip, a flask/canteen and a dagger on the other, and a revolver in a thigh holster. As long as other people have guns, you should too. And I hope firestarting methods go without saying.
Sorry for the long post; like I said, I'm rewilding my BOB too. Your post kinda forced me to consider what I have and need, got a little carried away thinking out loud. Hope I gave you some ideas though. But never take any advice without thoroughly researching it yourself, because knowing is half the battle. I may have no more than a high school diploma, but I've been intensively studying biology for a decade, since I was a still a young sponge soaking up information. That's why my brain simply has no room for society's bullshit. Never rely on what you or someone else has been taught, no matter how expensive your teachers were. Self-sufficiency is self-taught.