focus on the basics.
1) shelter, you need proper shelter from the elements, bad cold weather will kill you faster than lack of water or food, so tent, waterproof jacket and insulation, sleeping bag and a mat ALso bring matches, bic lighters, cotton balls and some rub alcohol in case you need to start a fire in a hurry
2) water, you can't carry enough water for 3 days, that would be more than 6 liters, you need to check for water sources and use chemicals to sterilize it, just in case
3) food, must be compact and high in calories, if you want to keep it simple don't bring stuff which must be cooked since that will require fuel, stoves and water.
4) navigation, plan the trip before, check the map, bring a compass if everything goes to shit and a map, they never run out of batteries, also bring a whistle for emergency signaling and light sources, a main one and a spare, with 3 times as many batteries you need.
5) inform at least 2 people at home of the route you guys are gonna take and how much time they must wait before calling for rescue.