Harvesting EXP: 3-4 exp per strike for mining stone. 3-4 exp per strike for chopping trees. 1 exp per gather of grass/egg/etc.
Building Craft Exp:
Campfire: 140 exp.
Sandstone Foundation: 96 exp.
Sandstone Wall: 49 exp.
Stonebrick Foundation: 785 exp. (T2: Level 20)
Stonebrick Wall: 413 exp. (T2: Level 21)
Wooden Box: 248
Armorer's Bench: 787 exp.
Furnace: 944 exp.
Blacksmith's Bench: 2801 exp.
Carpenter's Bench: 963 exp.
Tannery: 918 exp.
Firebowl Cauldron: 2231 exp. (Level 15 recipe, requires Level 20 Iron Reinforcement lol)
Temple to Religion: 1041 exp. Upgrading Temple: 14,509 exp.
Gear Craft Exp:
Hunting Bow: 103 exp.
Arbalest: 331 exp.
Stone Sword: 99 exp.
Iron Broadsword: 218 exp.
Flinthead Arrows: 52 exp. Ironhead Arrows: 62 exp. Coarse Tunic: 43 exp.
Coarse Pants: 31 exp.
Light Chest Piece: 97 exp.
Light Wrap: 77 exp. Wooden Shield: 70 exp .
Wooden Targe: 28 exp. (Triple checked this, this is accurate, literally gives less exp than the Wooden Shield craft!)
Iron Targe: 196 exp.
Repairing gear gives ZERO exp atm.
Kill Exp: All kills done on Tier 1 enemies, Tier 2/3 enemies offer greatly increased exp but are harder. For example a Tier 1 spider is 222 exp, but a Tier 2 spider is 876 exp and a tier 3 spider is 2,622 exp. Higher tiers have different colorations normally, take more damage to kill, and are more dangerous, but as demonstrated yield multiple times the exp.
Little Turtles: 222 exp, take one hit from anything. Rabbits: 219 exp, take one hit from anything. Big Mean Turtle: 441 exp. Antelope: 1,750 exp. Tested multiple times. Surprising. Imp: 221 exp. Crocodile: 877 exp. Emu: 2190 exp. Hyena: 440 exp. Rhino: 876 exp. Rockdog: Also 876 exp. Spider: 222 exp.
Human Exiles: Were not giving exp in single player for some reason during testing.
Crafting exp isn't just less good, it's absolutely atrocious considering the time investment. It awards a mere fraction of kill exp and even killing the easiest things in the game is more worth it then even tier 2 items. Even killing only imps, big turtles, and little turtles/rabbits is much MUCH better exp than T2 crafting. I do not want crafting EXP to even be close to the exp you get from killing. But right now crafting exp is incredibly low, so low it's not even funny. Killing should always be the best leveling option, but right now it is the ONLY option.
Some exp values like the temple upgrade exp looks like a big number but again keep in mind how much time it takes to get and refine all the resources for something like the temple upgrade. 3,500 stone, 2 hours of smelting, and 600 wood. You could get an entire level by killing during the time it took you to gather the ingredients alone and the temple awards 11% of the exp for level 20 > 21.
You can get significant amounts of resources by killing humanoid exiles. This includes things like stone, ironstone, plant fiber, coal, wood, bark, and more. In fact it's actually easier and faster to get some things like plant fiber and bark by farming the proper exile camps. On an small to mid sized camp camp I'd get roughly 200 ironstone + alot of other resources for example. A direct harvesting run for me would yield about 500 ironstone, but none of the other resources. This with me being in light armor and with an iron broadsword.
Some enemies do not feel as if their exp is relative to their difficulty. There are some standout examples even like Antelope, albeit if they fix their AI that may be more appropriate later.