§01
One currency, three demands
Amber pays for melee weapon upgrades, for projectile upgrades, and for the partial respec. That shared pool — not skill points — is the actual limit on how much you can experiment, and it is why respeccing casually is more expensive than it looks.
§02
Where upgrading happens
At a campfire, or at the workbench in the cleanse walker. Elemental bolts and arrows come from crafting manuals found in the field or bought from merchants, and enhancing a quiver raises how many you carry rather than their damage.
§03
Not yet written up
The three weapon types, the weapon lock system, the blue/yellow/green generator devices, the staged enhancement tiers and spirit stone duplication have all been seen but not played through. They get pages when someone has used them, not before.