I think this question can be answered in two ways: by considering the hierarchy of need or by treating it as question of personal enjoyment.
For me, hierarchy of need would be my main consideration, so it would have to be foraging skills - plant ID, seashore foraging, and small animal capture (but I'd have to be prepared to eat it raw . When man first stepped out all he had was a big stick to poke and dig with and he foraged for roots, berries, leaves and ate any grub and small animal he could get his hands on and scavenged. There's no point carving cooking and eating utensils, or starting a fire to cook on, or even building a shelter, if you don't have the skills to find food to keep you alive.
If it's a non-essential skill, not required to keep me alive, it would have to be the ability to sit quietly staring into a camp fire for hours
For me, hierarchy of need would be my main consideration, so it would have to be foraging skills - plant ID, seashore foraging, and small animal capture (but I'd have to be prepared to eat it raw . When man first stepped out all he had was a big stick to poke and dig with and he foraged for roots, berries, leaves and ate any grub and small animal he could get his hands on and scavenged. There's no point carving cooking and eating utensils, or starting a fire to cook on, or even building a shelter, if you don't have the skills to find food to keep you alive.
If it's a non-essential skill, not required to keep me alive, it would have to be the ability to sit quietly staring into a camp fire for hours