Kicking around some ideas

What would be the obstacles to colonizing the moon?  First, you get life support set up.  This requires assistance from Earth of course.  But over time, you want to minimize this because it is very expensive.  Therefore, the initial goal should be to get the moon base set up for life support on a long term basis. You need permanent shelter, water, oxygen and food.

Shelter will need to be built.  The initial shelter can come from Earth, but eventually you will want to build things from lunar materials.   How would you build shelters on the moon?  It may be possible to make them from yeast that can make plastics.  I read about plastic making yeasts recently on the web.  (see link)  These yeasts take the carbon dioxide the colonists will exhale and convert this into a useful building product.  Therefore, you want to collect the carbon dioxide as opposed to discarding it as waste.  It turns out that carbon dioxide is a very useful raw material in its own right.  In a very real sense, we are made of the stuff.

We may not be able to breathe carbon dioxide and live, but plants use it to make food that we can eat.  No reason to throw away carbon dioxide.  But what you are really doing is finding useful things to do with matter which is very expensive to launch from Earth.  The less matter that has to be launched, the more valuable the moon becomes.  This is because it is becoming more and more capable of sustaining itself without being resupplied from the Earth.  As food is imported, eventually it becomes plastics which can be used to make shelter.  That means fewer launches from Earth to support the colony.

But how do you grow things on the moon without water?  As with food, the initial supplies will come from the Earth, but ways must be found to extract water from the moon.  It turns out that this is possible.  There are small ( very small ) amounts of water in the lunar regolith. ( fancy way of saying soil )  By extracting this water,  it will become possible to sustain a lunar agriculture based upon lunar water supply.  Inasmuch as the water is hard to come by, it will be necessary to be very careful about how it is used.  As with carbon dioxide, it cannot be wasted.  Carbon dioxide from exhalation will be a supply for the plants.  Human waste can get recycled back into carbon dioxide or other organics which in turn can keep the cycle closed so that nothing is wasted.

Once you are able to solve the problems of shelter, food, and water, you can move on to becoming more productive.  At first you only be able to do limited number of things because of a lack of energy.  How to obtain energy?  As with basic life support, a starter energy system has to be imported from Earth.  But you want to be able to construct your own energy making systems with lunar materials.  How to do this?  Could you make solar panels with lunar materials?  This is possible.  Could you make a Stirling engine with lunar materials?  Stirling engines aren't new.  They were invented before steam engines.  One would suppose that a Stirling engine could be constructed with lunar materials on the moon itself.  It could be the first lunar power plant fully constructed on the moon to serve the lunar colonists.  Now the colonists can do things to increase their productivity even more.  The colony is becoming more self sufficient.

Perhaps the lunar colony can export something back to Earth in order to support itself even better.  What does the moon have that the Earth could want?  One thing that it has is energy from the Sun.  If you can make lots of solar panels which can produce far more than what the colonists need, you then have an exportable product.  But maybe that is getting ahead of oneself.  For the moment, perhaps it will suffice to be able to launch from the moon.  This will save the Earth from having to supply the moon with launching fuel ( and launchers).  You may want to learn how to do that next.  One thing the Earth could want is to stop having to subsidize the lunar colony.  If it can launch things on its own, it will be able to exchange with the Earth on a more equal footing.

Rather than thinking of the moon as a cost center, it can eventually be turned into a profit center.  If you want energy imports from the moon,  maybe you still want to subsidize it so that it can develop a real industry on the moon that can build and launch solar power stations into Earth orbit.   This may require the export from Earth of more sophisticated technology such as a complete launching infrastructure and manufacturing facility.
The manufacturing facility will produce the power station from lunar materials.  The launch facility will get it off the moon and into Earth orbit where it can produce energy for the Earthlings.  The moon is now supporting itself economically.

Besides energy, the moon can used to launching things.  It costs much less to launch from the moon than from the Earth.  But you have to have something that's on the moon that you want to get back from the moon.  Once you have that on a money making basis, the launch facility on the moon can move on to new projects.