Reddit mentions of Grizzly Gear Emergency Extra Large Thermal Sleeping Bag (Accommodates 2 Adults)- XL 84" x 36" NASA Mylar Waterproof Heat Retaining Survival Tent- for Hiking, Camping, Car and More

If you're looking at outfitting a 72 hour kit first before building out, there are some low cost ways to get that done relatively quickly.

• Food: Go to Walmart. They have Mainstay 2400 bars for about $5 each. Each bar weighs about a pound, requires no water to prepare, lasts for up to 5 years, and is good in temperatures ranging from -40 degrees F to 300 degrees F. Throw each one in a gallon sized ziploc baggie as they are not individually wrapped. That's a day's worth of calories per bar, or two if you eat under your calorie requirements. Get three of them in the bag along with a few multivitamins and call food covered.
  
  
• Water: Pick up 2 flats of bottled water. That's like $3-$5 each. Drink from one of them, when that one empties, replace it and drink from the next oldest one. Your water will always be relatively new then, and a flat of water is more than you're going to carry on your back anyway. If you need to grab and go, you can do it easily. You'll also have excess water if you need to throw it in the car. Longer term, get yourself a Sawyer Water Filter. Stay away from Life Straws. The Sawyer allows you to refill bottles from contaminated sources and then filter them out into other bottles. This is critical for cooking and allowing movement away from water sources. The Life Straw does not do this. These are also available at Walmart for around $20.
  
  
• Self Defense: Get yourself a camping knife of some sort. I like Ka-Bar's a lot, but they're a bit expensive. Kukri's are also nice, but of wildly varying quality and not great for fine or point work. A good knife is a multipurpose tool, and you can get one fairly inexpensively when you're just getting started. Just make sure it has a good edge on it.
  
  
• Shelter: There are better options, but for staying cheap when getting started, grab some Mylar Blankets and maybe a Mylar Sleeping Bag. Both can be acquired inexpensively and give some options you might not have otherwise. The Mylar Blankets you should probably always keep around. Add some duct tape to the bag and they can make an easily constructable temporary shelter given a little resourcefulness.
  
  There. For less than $100, and maybe less than $50 depending on what you get or already have, your 72 hour kit will be at a base level, ready to get you out of the door. Of course first aid stuff is a smart call, and you can get as finely detailed and over packed as you like with a BOB, but as a base this will get you out and moving for a few days.
  
  As a recommendation for getting started after that pack, grab a 100 lbs of white rice. Get it divided across 3 clean, food safe, 5 gallon buckets with lids. It'll keep better wrapped in Mylar bags, but you can have oodles of calories that will still last for years for less than $50 without that. It's a smart way to start prepping a food supply.