Well, if large swaths of ice are found on the moon (as studies suggest), you would simply need to mine the ice and it would provide O2, water, and humans would provide the Co2 for plant growth. A preliminary base would do very well on the pole, where both solar power and ice are plentiful.
Ilmenite - which is plentiful on the moon - provides excellent titanium, iron, and oxygen when broken down.
Anthorite - also plentiful - produces silicon, calcium, and oxygen.
The only thing really missing would be nitrogen and meat. The moon, however, and the technologies created would definitely allow people to leave to other planets within a decade or so. We should have never left the moon, but we simply didn’t have the technology to have a sustained presence in the 60’s - we do now.
Again look at the costs the Apollo program cost about $24,000,000,000 in 1970 dollars. It returned 841 lbs of rocks, and if they could have brought back more they would have. That works out to $1,783,000 per OUNCE, Titanium iron and O2 are a lot cheaper right here. If we allow for inflation, then returning moon rocks today would cost about $4.5 million per ounce. There isn't ANY raw material worth that much - in fact I'd have a hard time coming up with anything worth that much.