But there isn’t exactly a lot of readily available resources on the moon, so until that changes your just paying to lift stuff twice. Water may be an exception to this?

You can use electricity to split water into hydrogen and oxygen, aka, fuel. Finding an underground ice lake would provide lots of fuel, and save on lifting the heaviest, most important substance for manned exploration from earth.

Water takes a lot of energy to split. Take a small size as a pot on a cooker with a litre of water.

Just to get that litre to bubble takes constant. Heating for minutes or imagine how long it would take to boil all that water away.

Sure you'll have a lot of fuel but its not easily accessible.

How much energy does it take to get stuff from the earth to the moon though?

Is it that much less than leaving earths gravity all together?

The point would be that the stuff we would use to explore/colonize the solar system would be made on the Moon with a relatively low investment in stuff having to be send there to set up the base and mining/production process. Ideally only humans themselves and a few personal items would be send up from Earth, with everything else having been produced in orbit.