Golden Amber in Immortals Fenyx Rising is an important resource that will allow you to upgrade your potions at the Cauldron of Circe. You will need to keep an eye out for this rare resource, and also be careful, as it tends to be in more dangerous areas.
The resource can be farmed throughout the game, so make sure you always have your eyes peeled for it as you explore the world.
The best source of Golden Amber are glowing trees that you can find throught the game. As you walked through wooded areas, keep your eyes open for trees, or trees stumps, with small golden motes floating around them. If you cut these down with your axe, you will find a Golden Amber inside.
The only downside is that these areas will often has some large, dangerous monsters in them like a bear, or terrifying demons. This makes it dangerous to go in after them, but it is worth it for the extra potion upgrades that you can get.
Opening chests, many of which will be well hidden, is a great way to find this resource. You can find chests as you explore the world, and using your farsight by pressing the right thumbstick and then scanning the area can reveal more locations.