Use the NPC Gear table and compare to the listed gear actual value
“NPC gear” indicates the monster has treasure as normal for an NPC of a level equal to the monster's CR.
A Goblin is CR 1/3. The NPC Gear table has no entry for levels lower than 1 but it's easy to take the amount for level 1 (260gp for a Basic NPC, which most monsters should be) and divide by 3 (about 86gp)
The Goblin entry lists its NPC Gear as:
Treasure: NPC gear (leather armor, light wooden shield, short sword, short bow with 20 arrows, other treasure)
Totalling up everything (except "other treasure" of course) gives a value of 54gp. You could thus assume you have 32gp (86-54) of wiggling room. Either give them about 30gp or an item worth about that much.
Budget treasure based on total XP
But better yet, I'd suggest budgeting treasure based on the total CR of an encounter, or even of all the encounters of your adventure (or sections of it if it's really long).
If you plan to have the following encounters:
- 3 Goblins (135 XP each, 405 total)
- 2 Goblins (270 XP) and 1 Goblin Dog (400 XP) (670 total)
- 1 Hobgoblin (200 XP), 2 Goblins (270 XP) and 2 Goblin Dogs (800 XP) (boss battle?) (1270 total)
This totals up 2345 XP. If you look at the Experience Point Awards table, you will see that this is equivalent to a CR of 6 if it was one big encounter.
To aid in placing treasure, the amount of treasure and magic items the PCs receive for their adventures is tied to the Challenge Rating of the encounters they face
Table: Treasure Values per Encounter lists the amount of treasure each encounter should award based on the average level of the PCs and the speed of the campaign's XP progression (slow, medium, or fast). Easy encounters should award treasure one level lower than the PCs' average level. Challenging, hard, and epic encounters should award treasure one, two, or three levels higher than the PCs' average level, respectively.
Admittedly, I do not follow this perfectly. I prefer to align the CR of an encounter with the Average Party Level listed in the Treasure Values Per Encounter table. I'm pretty sure "challenging, hard and epic" mostly corresponds to CR = APL+1, +2 and +3 anyway.
So, our total XP equivalent to a CR 6 encounter ? Look up the APL 6 line in the table and check the treasure amount for your desired track speed. Let's say you go with Medium progression speed, that's 2000gp.
Once done with all these encounters, the party is expected to have earned, somehow, 2000gp. That's your treasure budget for all these encounters. Now you try to spread this value across all of them. You can split evenly, or make one big treasure hoard the PCs get to after all these encounters, only earning meager or no treasure along the way.
Do take into account NPC Gear value if your players usually pick it up and sell it. In our case, if we expect the PCs to sell every piece of gear they find, we should remove 54gp per Goblin (their NPC Gear value we calculated earlier), 125gp per Hobgoblin and nothing for Goblin Dogs as they have no default treasure at all. That's 54 x 7 Goblins + 125 x 1 Hobgoblin = 503gp of NPC Gear, leaving us with 2000 - 503 = 1497gp as actual treasure besides NPC Gear.
Again, how you "use up" this budget is up to you. You can spend it on upgrading NPC Gear, turning a regular weapon into a Masterwork version (usually +300gp value), or adding various treasures such as potions, gems or simply gold to a treasure chest or some loot bag lying in the goblinoids' lair.
If you add to NPC Gear beyond their Bestiary entries, keep in mind the NPC Gear table. Your Hobgoblin, at CR 1/2, isn't expected to be carrying much more than 130gp (260/2) in gear. If you go way beyond, things might get tough for the party.