I'm imagining the lists will vary for people. A lot of it depends on luck of the seed. For me...

EASY:
- wood
- stone
- resin, guck, tar
- leather scraps
- core wood
- fine wood
- trophies (other than the stone golem)
- iron, dark metal, tin
- farmed foods

HARD :
- silver, copper
- freeze glands (#1)