Okay. This is how you put together The Adventure Sack.I have done no shopping around on this, but I am fairly certain almost all of this can be had cheaper than the sources I am finding. Better yet, learn more, you'll carry less.
Get a small to medium sized backpack, the more incongruous the better. Don't get flashy neon Rescue Ranger stuff. As a general rule, it's easier to make yourself seen than it is to hide, so again, get something that doesn't stand out. Make sure it is serviceable. This is not the same thing as " new". If you have been a student in the past ten years, you probably have at least one hanging around that will fit this bill. You are better off with something older and more familiar, IMHO. Do not be afraid to modify this bag. Reinforce stitching with fishing line or disassembled paracord, melt frayed ends with a lighter, tape down buckles that might rattle. You don't set out trying to look like a Chinese bandit, but almost inevitably , good kit does.
Next, a knife. Much has been said about this. Too damn much. I am a knife guy. Most "survival knife" stuff is bullshit. You can get stuff like all day, for <$30, and it will do just about anything you want it to.
Also, you don't fret about your favorite $900 Randal custom mammoth killer hollowhandle bowie mostrosity when you have to cut wire with it.
Right behind that, a multitool. You can go apeshit here, or you can get a that works really well for less than a steak dinner. This and the next item may be the most used things you will carry.
A good source of light. You can get a Surefire that will set you back the cost of a light rifle, or you can get a half dozen little AA-LED lights and squirrel them all over your pack for about $20. Rotate them out by using them when ( duh) you need light. Head lamps and weapon mounts and IR goggles are great. But you won't need them. Small lights can have a bandanna wrapped around the handle and carried in the teeth in a pinch. Bam, headlamp.
Third, fire. Carry multiple types of fire generators, and know how to use those you aren't carrying as well. Disposable Bics everywhere there is a ziploc ( more on that later). I'm a big fan of the because they are so light, cheap and unobtrusive that there's no reason not to have them. A ziploc of cotton balls generously smeared with petroleum jelly makes a great fire starter. Carry multiple methods. If it's designed to start a fire, wrap it so it is waterproof. Two ziplocs and some tape( if you really, really want to be anal about it) will do unless you are an Navy SEAL. You can make lifeboat matches by coating Strike Anywhere matches in harder types of parafin, or you could just buy some
Water. For this, you need to ideally have some sort of metal container that can boil water in it. This is nice to have and can be had for fairly cheap if, again, you go to military sources. The old is hard to beat, IMHO, and can usually be had for under $10. A stove for that can be rigged up out of an old can, a rim from a car, green sticks and probably an erector set. None of this is rocket science, jerky.
It is not enough to be able to boil your water, however, This is not always convenient or even possible. There are cheap, SHTF limited use that will do well enough, and you can always carry a bottle of cheap .
Next, medical. If you don't know anything about this, you owe it to yourself and your fellow man to get at least Red Cross certified in first aid and CPR. If you can swing it, get First Responder training ( Google). There are tons of resources on this, and it works inverse of other survival gear; the more you know, the bigger your kit gets. I can only go into so much depth on this because it has to be keyed to your level of knowledge. At the bare minimum, though, get a that doesn't take up much room. Big note: it doesn't matter if you carry enough stuff to film a MASH remake, if you don't have that dung beetle extract for your scrotal meningitis, you are boned. Tailor this to your personal needs as well as what you know how to do. My blowout kit fits in a 6x4x3" pouch and will handle GSW/perforated lung. It also has two braces, knee and ankle, and my Gas-X and lactobacillus supplements for those times when I am forced to eat processed foods that usually contain milk.
And on that note, bring some toilet paper, most of a roll, tube extracted, in a big zipoloc , taped shut. You never know.
Shelter. I don't carry shelter, I build it, because I am not a turtle. I don't give a damn if I am out on the open plains, I am digging in like a damn groundhog. Carry ready cordage- even if you can make your own, it's time consuming, and you may not have a lot of time. A fifty foot span of is compact, handles 550 pounds free hanging , and is cheap. It can also be disassembles, using the inner white nylon threads for everything from sutures to making fishing lures. The outer casing is still usable, only has less tensile strength.
Having said that, carrying a little mylar type is a good thing. Lightweight, cheap and doesn't take up much room. Might be nice in a pinch. I don't carry one, but you might want it some cold night.
You can put together a really good little fishing kit, complete with lead weights, hooks, line and even a sealed bit of bait that will fit in an Altoids tin. You would be amazed how many little crap waterholes have fish in them. Not to be overlooked.
Tape. The trick now appears to be tape wrapped around a credit card. I always just used a roll halfway and collapsed the carbboard. Again, put it in a ziploc. I actually have a couple of types of tape, because that's just the improvisational flair I have.
Carry a couple of dollars in quarters, taped into a roll. Can be used as emergency tolls/phone money( assume you can find a coin operated phone) or can be held in a fist and used to knock the taste out of somebody's mouth.
Get a travel pack of good quality hand wipes in a hard travel case. This is another often-used item, which is good, because they may need to be rotated out. Get a spare set of all keys you own and put them in the bag somewhere they won't make noise. A badanna is good to have, and I have a leather shoelace wound up that can be used to effect rapid repairs. A few zip ties, rubber banded together, and a tin of hard candy or breath mints. Because fear will dry your mouth out and sometimes wintergreen is just the thing. A cheap sharpening stone.
Last thing is a small paperback book. First, because you may have time to kill. Next, the pages can be useful. Think about what you carry. I have the military FM on survival and/ or Aurelius' Meditations, just the sort of thing you want in an emergency. A notepad and pen, and a permanent marker to round it out.
Again, this is a generous basic kit. I don't carry a lot of this. Some things I carry more than I need for me, and I have tons of space in my bag for things I pick up along the way. This is a key point; if things get ugly, always, always be looking for things that will be useful to you. It's a delicate balance between utility and mass, but playing it right has rewards.
Much else can be modified based off of your environment and even time of year. Notice I didn't put stuff like changes of clothes or a spare wool sweater ( retains heat when wet), because I am in Florida. There are only about twenty days a year where I would even thing about starting a fire. If you spend most of your time in a city, think accordingly. Maybe carry a concentrated meal ( a broken down MRE works fine) for those times when you are locked in elevators, I don't know. The whole point is adaptability. The items mentioned give a basic level of utility that can take care of most issues before they become issues. You are more likely to have to use this stuff after a blowout or a paper cut than a nuclear war.
Don't know what it is, but I'm agin'it.