Keep in mind that playing on a higher difficulty level does *not* increase the chances of a Goblin spawning. It does greatly increase the amount of gold they drop, and especially the amount of gold you find inside of The Vault if you get lucky and find that coveted yellow portal, so it’s best to farm goblins on the highest difficulty level you can reasonably handle.
Where to find Goblins?
When Patch 2.1 launched the best place to farm goblins was in the Act One Halls of Agony level 2, since there was always a Treasure Goblin somewhere on that not-very-large level. HOTFIXED!
So now it’s more random, and the Halls of Agony 2 is no longer recommended since it’s not a great layout to farm. The most popular areas now are mostly in Act Three, and they are the various Tower of the Damned/Cursed levels, since they’re fairly small and are circular or spiral in layout, so they can be completely “explored” fairly quickly. The Core of Arreat (last area in Act Three) is also good as it’s a straight shot and is narrow, making for fast searching.
Act One has some good levels as well, since the outdoor areas there (Leoric’s Hunting Grounds and the Northern Highlands) seem to have a high Goblin spawn chance. I’ve seen other players recommend the Cave of the Moon Clan dungeon below the Southern Highlands, and oddly, the Highlands Passage, which is that small outdoor area between Halls of Agony 2 and the Jail, where you find the Warden.While playing in general, it’s a good idea to poke your head into all those little dungeons. The single room cellars you see early in Act One, the little houses under early parts of Act Two, etc. Those take just seconds to check, and it’s not uncommon to find a Goblin in them.
The funniest goblin hunting suggestion I’ve seen anywhere was a guy on Reddit claiming to have found a pair of them in Leah’s bedroom, inside the Inn in Act One town. His claim excited a lot of debate, but it was not reproduced and eventually ‘shop experts took a magnifying glass and could tell from some of the pixels that it was a fake.
Which is a pity, since I can think of any number of inappropriate jokes regarding Treasure Goblins in Leah’s bedroom.
Click through for more on goblin strategy, and a clever trick/exploit that allows a patient player to fight an infinite number of goblins, one at a time… but is probably not worth the trouble.