Another way to look at it revolves around the rule of threes: You can survive three minutes without air, three hours without shelter, three days without water, and three weeks without food. The rule is hardly absolute but it gives you a framework for setting priorities.
Yes, this is what I used:
Air - can be caused either by an injury (most likely) or a dangerous chemical gas (less likely unless it is smoke). Two options get help or get out. Get help signalling, get out navigation and tools to make sure obstacles can be dealt with. I suspect that if you are injured, you will be lucky to press a button of a beacon or, if there are people around you, they can use your kit to provide first aid and call for help
Shelter layering, but it needs to be compact
Water - it is heavy and there is little to improvise, you either need to carry it with yourself, or have a filter. If situation presses hard, then I will drink as clean water as I can get and then spend time in a hospital.
Food I tried to check survival statistics about starvation and could not find it. I suspect that it is not that frequent in non-conflict areas. So, I feel snares, fishing kit etc are good for keeping you busy and additional building material, but thats about it.
I am not discussing weapons because there is a higher chance police will stop and search me in any country I visit than actually end up in a situation when it becomes essential.