In addition to exploring and stealing or looting from others, you and your tribe members can build things of your own. At a minimum, you’ll need to feed yourselves, and build a lair to house the tribe and any tools and facilities you need. Here are some example things goblins can do:
Survival DC 15 to feed yourself while moving at half your overland rate. You can feed one other person for each 2 points you succeed by.
You can get a +4 on the check by spending all your time hunting, and not moving.
Moving and hunting or hunting full time counts a hard work for morale purposes. Hunting half time without moving (no +4) is light work.
Two goblins can dig out a 10’x10’x10’ room from dirt in a single day. One goblin per 100’ of distance to the tailings pile is also needed, to carry the dirt away. This assumes good tools – wheelbarrows, picks, and shovels. That rate is definitely hard work! Half that for light work.
Limestone, sandstone, or other soft stone
Double the figures for dirt, just to move the stone after it’s been broken up. Breaking up 10’x10’x10’ of stone takes 3 goblins 5 days of hard work.
Basically impossible to dig out by hand. Skilled miners can make slow progress by fire-setting.
Use a modified form of the Craft skill rules from the PHB.
Labor is measured in money, even if there’s no actual payment involved. A Craft check for a full day’s work will yield (check DC * check result) cp worth of progress. Goblins consider a 5 day work week onerous, and working a full day every day to be an unacceptable level of industry.
Unlike in the book, there are no materials costs directly involved in the craft check math; those are handled separately, and vary based on the task.
Craft can be used unskilled, but most unskilled Craft checks are made at -4.
These same rules also apply to Profession skills.
Unskilled work uses a Strength check in the place of a skill check, but is otherwise identical.
Exact labor costs for various things can be found in the Industry rules.
Your PCs are the most talented of your generation, and the obvious and acknowledged leaders of this group. But your tribe members can still do things reluctantly or enthusiastically, and if you push them too far, they’ll buck your authority and eventually rebel.
I have some mechanics for tracking tribe morale, but since they’re somewhat subjective and your characters can’t know the current state with perfect accuracy, the specifics will remain a DM secret.
In general, goblins like leisure, comfort, good food, alcohol, wealth, and causing mayhem. They dislike hard work, danger, privation, and being pushed around by outsiders. They like winning fights and dislike losing them, but are fine with successfully running away.