If the moon had an atmosphere, would that make it easier or harder to send people there?

Depends on the thickness.

If it's a thin atmosphere, similar to what Mars has, it'll make it much harder to get there: you can't ignore it (you'll burn up if you do), but you can't use it to slow yourself down either (it's too thin). A thin atmosphere won't help much with temperatures either, but it would be better than having no atmosphere at all. Even a thin atmosphere offers a bit of protection from radiation, which is helpful.

A thicker atmosphere would be more useful. It would retain heat better, meaning less temperature variation. It would also be more helpful in slowing down incoming craft: a parachute is much more practical in a thick atmosphere than a thin one. On the other hand, a thick atmosphere would make leaving harder. (The most helpful thing would be an ocean: that's what we use currently. We just crash all incoming spacecraft into the sea.)

Any atmosphere will have storms. The gas giants have immensely fast winds and humongous electrical storms, while Mars has sandstorms that last for months on end.

Well it would depend on the type of atmosphere obviously. Titan has an atmosphere thicker than Earth's, even though it's only 50% larger than the Moon. So the density of the atmosphere would matter. In all though it would make landings much harder regardless. The one benefit would be that if the atmosphere was thick enough you could use parachutes to slow down. But parachutes aren't light either and since the Moon has very light gravity you can use rockets easily for this. So rockets are much better. Plus you'd also have to have a heat shield to enter the atmosphere. That isn't light either. And you'd have to make the lander heavier because it would have to be thicker. The Apollo Lunar Modules had skins in places thinner than a soda can. If they were having to survive winds and atmospheric pressure, and an entry through an atmosphere, that just wouldn't be nearly strong enough. Plus when you blasted off to return to Earth you wouldn't just be fighting gravity, you'd be fighting atmospheric resistance also. So not only would the lander have to be heavier and thicker, it would also have to be somewhat aerodynamic. Even if you were talking about a very thin atmosphere you'd still need a heat shield, but then you wouldn't have the benefit of being able to use parachutes to slow down. But you'd still need to make the lander at least a little beefier. We could still do it of course. But it would be a good bit more difficult and more expensive.

Easier to land, and easier to build a base there, but harder to take off. You can use the air to land without using fuel, using parachutes or gliding with wings. The base would have air and not have to be sealed air tight; it could be just regular buildings. But air drag makes it harder to take off. However if there was air they could be water too, and then you could make fuel on the Moon. This would make it MUCH easier to go and come back. If there was no fuel in Europe, airline flights from the America to Europe would be REALLY hard, because the planes could not refuel in Europe. They would need to carry enough fuel for the whole round trip which would make the plane too heavy to carry any passengers. That is what a big problem with space travel. We can't refuel on the Moon or Mars. Actually we COULD refuel on Mars, because there is air and water. Many plans for going there include making fuel on Mars. But to do that you first have to get there and then build a fuel manufacturing plant. And since Mars is so much farther away than the Moon, and takes so much longer to get to, we haven't done it yet.

Unless the atmosphere protected from Radiation (like Earths) than it would just make landing and taking off way harder., So I'm ganna go with it would make things harder.