Mastery is the number Graveyard Keeper 2 checks before it lets you swing at a rock, plant a seed, preach a sermon or run a bench, and it is the number the game explains least. Two different refusals look almost the same. One says you are not skilled enough, and the other says you are holding the wrong thing.
They are the same problem. Your mastery in a job is built from several sources that add together, and only one of them is the level you spend points on.
Five tracks, each named after a job
The game keeps five mastery tracks and colors them: Building in orange, Smithing in red, Farming in green, Book writing in yellow and Anatomy in blue. Every gate in the game names one of the five, so a Smithing level does nothing for a garden bed.
Each track carries exactly five levels you can buy, worth one mastery each. That is the entire permanent ladder for a track, and it is worth knowing early, because five is a small number next to the requirements you will meet later.
Your tool belt is most of your mastery
Ten families of tool carry a mastery rating, and each family feeds one named track and only that one. The 
Rusty Axe, 
Rusty Pickaxe, 
Rusty Hammer and 
Rusty Shovel are all worth one, their bronze versions two, iron four and steel six.
The rest run shorter. Bronze tools, the Butcher’s Kit, the Starter Alchemist’s Kit, the Primer and the Bronze Talisman all start at one and climb to four at Steel tools, the Master Surgeon’s Kit, the Glossary and the Golden Talisman. Fishing rods are the exception with five rungs: one at the Basic Rod, up to six at the Pro Rod, and eight at the Master Rod that nothing in the game hands over.
Five levels is the whole permanent ladder for a track. A Steel Pickaxe is worth six on its own, so upgrading the thing in your hand moves the number further than an afternoon of inspiration points does. When something refuses you, check the tool before you go shopping for levels.
A 
Copper Nugget is the cleanest example of the trap. Its vein asks for two in Smithing and will not let you swing without a pickaxe in hand, and a pickaxe feeds Building. The tool the game makes you carry does nothing for the number it is checking.
A hammer is what moves it. A Rusty Hammer on the belt is worth one Smithing and a 
Bronze Hammer is worth two, and either one sits there while the pickaxe does the digging.
Every tool declares its own track and keeps to it. Axes and pickaxes feed Building, hammers and the small tools kits feed Smithing, and shovels and fishing rods feed Farming. Surgical kits and alchemy kits feed Anatomy, and books and talismans feed Book writing.
Your belt holds fourteen items and the game adds up every one of them that feeds the track being checked. Equipping a second pickaxe puts the first back in your bag, so one tool per family is the limit, but two families feeding one track do stack. A 
Steel Axe and a 
Steel Pickaxe carried together are worth twelve Building.
Every track has a best pair. A 
Steel Hammer with 
Steel tools makes fifteen Smithing, and a 
Steel Shovel with a 
Pro Rod makes seventeen Farming. Anatomy and Book writing are the poor relations, because their four families all stop at four rather than six: the 
Master Surgeon’s Kit with the 
Good Alchemist’s kit, and a 
Glossary with a 
Golden Talisman, both land on thirteen.
Polished Bronze asks for five in Building at the 
Woodworking Workbench, and a player stuck at four cleared it by making a 
Bronze Pickaxe. Nothing about that recipe involves mining, but a pickaxe feeds Building wherever you are standing, and the bronze one is worth two where the rusty one was worth one. A 
Bronze Shovel would have done nothing at all, because shovels feed Farming.
Points come from experience, and there are barely enough
Inspiration points are the currency, one color per track, and you earn them by doing the thing rather than by buying it. The game says so in its own tutorial.
Performing various actions earns different inspirations. Inspiration points can be spent on perks and increasing talents.
The game’s Inspirations and Talents tutorial
An inspiration is a counter with levels: mine three copper veins, then ten, then twenty five. Completing a level pays experience into that track rather than a point, one for most levels and two for the deepest. Experience is the thing you collect, and points are what it buys.
Experience converts on a rising ladder. The first point in a track costs two experience, the second three, the third four, and every point after that costs five.
That makes the arithmetic exact rather than generous. The five tracks hold 382 inspiration levels paying 453 experience, which buys 95 points, against 95 things to spend them on: 25 mastery levels and 70 perks. One point for every purchase, with nothing spare.
Experience never crosses tracks, so a surplus in one is stranded there. Farming earns eighteen points against twenty one nodes, which leaves it three short however you play.
Building finishes three points clear, Anatomy two, and Smithing lands on exactly eighteen for eighteen. Book writing looks one short at nineteen nodes, but its last one is hidden and nothing in the game reveals it, so eighteen points meets the eighteen you can reach. Spend Farming on what you want rather than on what comes next, because you will not be coming back for the rest.
Perks add mastery, but only for one material or one bench
Perks are the other 70 nodes, and a good number of them add mastery under a condition. Fissure Finder gives two Building when you work with stone, Tempering Expert two Smithing when you work with steel, and Master Embalmer four Anatomy at an Embalming Table.
Conditional mastery is how the later requirements get met at all. Five levels and a steel tool come to eleven, and the top of the craft ladder asks for sixteen, so the gap is closed by a perk that only counts when you are doing that one job.
What the number gates
In the world, most things ask for very little. Two is the commonest requirement by a wide margin and it covers the trees, stones and veins around your house, with one and three close behind. Anything above five sits on barely a dozen objects in the whole game.
The number keeps working after it lets you through. Each swing takes off your mastery divided by what the object asks for, rounded down and capped at three, so a gate you meet exactly is a gate you clear the slowest.
A large linden asks for five Building and holds six cells, which is six swings at four energy each. At ten Building every swing takes two cells and at fifteen it takes three, so the same tree costs eight energy instead of twenty four.
Benches are steeper. 220 crafts sit at mastery one, and from there the ladder climbs to sixteen for the last prayers and the best garden beds.
Items carry their own requirement, shown as “Required mastery” in the tooltip, and this is where the tracks stop behaving alike. Farming gates 39 items, from the Roach at one to the Elder Catfish at eighteen, with Wheat seed at two and the best seeds at sixteen. Book writing gates 73, mostly prayers, up to Prayer for Old God at fourteen.
Building and Smithing gate no items whatsoever. Both do their gating through the world and the bench instead, which is why a blacksmith feels limited by their anvil and a farmer feels limited by their seeds.
Fertilizer and buffs are the two that do not last
A garden bed is the one place mastery can be bought outright. Fertilizer adds it to the bed rather than to you, from one for 
Peat up to eight for the best of them, which is how a sixteen mastery crop is grown by someone who has five levels.
Buffs are the other temporary source, worth one, two or three in any of the colors for as long as they run. Neither shows up in your character screen as a level, and both count when the game does the check.
Graveyard Keeper 2 Mastery FAQ
What is mastery in Graveyard Keeper 2?
A required skill level, kept as five separate numbers rather than one. Building, Smithing, Farming, Book writing and Anatomy each have their own, and a gate always names one of the five, so a Smithing level does nothing for a garden bed.
How do you increase mastery?
Four ways that add together: levels bought with inspiration points, five per track at one point each; better tools, worth up to six each and stacking when two families feed the same track; a perk that adds mastery for one material or one bench; and fertilizer, for a garden bed only. Tools are usually the fastest of the four.
Why does it say Not enough mastery?
Your total for that track is below what the thing asks for, and the total counts every tool on your belt that feeds that track. Check the belt first: a steel tool is worth six, more than all five levels put together, but only for its own track. A better pickaxe does nothing for a Smithing gate.
What is the maximum mastery?
Five levels per track is the whole permanent ladder, and the best pair of tools stacks on top. Building and Farming both reach seventeen, Smithing fifteen, and Anatomy and Book writing stop at thirteen. Conditional perks push one job higher still, which is how the requirements of sixteen at the top of the craft ladder are met at all.
Can you spend inspiration points on the wrong thing?
In Farming, yes. Inspiration levels pay experience, and experience buys points on a rising ladder that settles at five each, so 453 experience becomes 95 points against 95 nodes. Farming ends three points short of its twenty one, and experience never crosses tracks, so a surplus in Building cannot rescue it.
