My list is aimed purely at those starting out, I have tried not to be prescriptive as everyone has their own aims and preference when out and about.
1. When starting out, most people will need to purchase a lot of kit at once to enable them to get out there. After that we refine our kit as we refine our ideas over time. Many of us go through a weird cycle of buying kit, selling kit and after several years and iterations of our setup we end up re-buying stuff we got right at the beginning. The hard part is to explain to someone which items they are buying to get started and which items should be kept.
2. General camp admin is really good to know as it makes your whole experience better when outdoors, you know where all your stuff is, you are less likely to lose anything, you can pack your gear away faster and it makes a big difference to how you feel. I'm not one to force my will on others but some photos I see of peoples little areas look like an explosion at a jumble sale with stuff strewn over a wide area. as well as how to manage yourself in the woods, other basic camp stuff like where to go to the loo, to check for overhead hazards and to evaluate a site for other concerns like where water will run after a heavy downpour. These things take quite a while to learn typically because we all just use trial and error which seems a bit mad when we will happily go on course after course for making a spoon.
3. Knots and the quick and effective ones to learn and how to apply them properly. The subject is so big that it can get overwhelming but a few simple knots that really are mastered can make pitching tarps, hammocks and tents easy, can provide secure lashings when making tools or furniture and improve your safety and comfort a great deal.
4. Cleaning, sharpening, maintaining and safely using your cutting tools. Basics starting from terms used to describe knife shapes and blade profiles and why they are favoured. How to safely carry your sharps through uneven terrain and other basic things such as how to stand or kneel when chopping with an axe, how to safely carve with a knife. For sharpening, it is good to show methods that are consistently good and that can be picked up quickly without having to purchase much kit and stop way before adding complexities such as true honing and polishing and working with exotic materials.
5. First aid and hygene on a very basic level with things likely to happen... twisted knees and ankles - how to check that nothing more serious has happened, how to deal with minor burns and cuts and how to keep yourself not only alive but clean in the woods. How to check other people out for all of the above, especially if you travel with children or pets that might not be able to articulate symptoms to you like what a drowning person actually looks like in the real world and what the start of hypothermia looks like. Again, basic things that can be taken further over time.