I assume we're talking only about passion (honestly I don't think I've ever levelled up a skill without some passion).
Based on the way I pick pawns I would say..
easy:
-growing
-cooking
I think growing and cooking are among the easiest, but perhaps that's because the associated thresholds are relatively low. Cooking you need 6 for fine meals (or something like that?) so a pawn with 2 but passion will be there in no time. Someone will probably get food poisoning, but that's never THAT bad.
Similarly growing needs 8 for healroot (I could be wrong about that too!) so even a pawn with only 4 but good passion will learn it after planting a few fields.
hardish:
Crafting and art are a pain because you want them as high as possible. Sure even a low skill pawn can learn it, but they're slow and produce poor quality stuff while you wait for them to improve.
super hard:
-social
-medicine
-(animals)
I feel like if you don't have a pawn that's good at these to begin with, it's probably never going to get there. There aren't many opportunities to train them - or in the case of animals there is a risk to trying to train them up. If you start with a cat for example, you can't train that and any other training sends your pawn half way across the map for ages and risks getting attacked. obviously training medicine on a low skill pawn is incredibly risky/difficult. Social you only do twice a day so it trains slowly and you have to have a prisoner who you are feeding and waiting for ages for them to be recruited.
I don't have strong feelings about the other skills.
Based on the way I pick pawns I would say..
easy:
-growing
-cooking
I think growing and cooking are among the easiest, but perhaps that's because the associated thresholds are relatively low. Cooking you need 6 for fine meals (or something like that?) so a pawn with 2 but passion will be there in no time. Someone will probably get food poisoning, but that's never THAT bad.
Similarly growing needs 8 for healroot (I could be wrong about that too!) so even a pawn with only 4 but good passion will learn it after planting a few fields.
hardish:
Crafting and art are a pain because you want them as high as possible. Sure even a low skill pawn can learn it, but they're slow and produce poor quality stuff while you wait for them to improve.
super hard:
-social
-medicine
-(animals)
I feel like if you don't have a pawn that's good at these to begin with, it's probably never going to get there. There aren't many opportunities to train them - or in the case of animals there is a risk to trying to train them up. If you start with a cat for example, you can't train that and any other training sends your pawn half way across the map for ages and risks getting attacked. obviously training medicine on a low skill pawn is incredibly risky/difficult. Social you only do twice a day so it trains slowly and you have to have a prisoner who you are feeding and waiting for ages for them to be recruited.
I don't have strong feelings about the other skills.