I feel like I am a sporadic grinder (I managed to complete the event pass), but I too am struggling with moonstones. The vast majority of my current stash is from achievements. I have 400MS and I'm saving up to get a Vespen.
My main complaint is that by now there is no way for the casual/newer player to make MS on the flea market. By this time there should be enough MS around to start to stabilize the economy, but there's no reliable way to get them even through the flea market.
In FR, a new player can grind for stuff and improve their cauldron and sell mats/items and gain gems that way. Here I struggle to keep up with my own demand for Bone Paste (wheels, picks, and MS) and Bone Paste on the flea market is dirt cheap. I have no time or mats to make anything else in the craft shop that might sell for more, and from my experience there isn't a demand for them. I got excited with the achievement silk things, but those are ALL apparently soulbound so you can't sell them.
The cooking system badly needs a revamp; it's not worth my time and effort to cook higher quality food, and a full stack of lower quality food sells for dirt cheap on the flea market.
Basically all the MS are going to float around between those who buy them and those who make custom apparel, and those of us who can't do either are stuck. There is no market for wolves, and leveling takes too long for "exalting" to be a money maker, so basically all the ways I make money on FR don't work here.
I think the Icerun event was a step in the right direction; I may be able to make some MS off those apparel items eventually. But so far I'm still pretty discouraged that even though I work hard, the MS/pebble ratio keeps going up and my dreams of a Vespen keep getting farther away, to say nothing of getting the rest of the KS companions.