There are a couple of ways to get a moonstone
- Have mom buy you one by saving money.
- Search for one in the Ruin of Alph
- Get one on top of Mt.Moon (on Monday nights only)
- Search for one in Tohjo Falls
- Or use the Pokewalker.
(Volcano Path (5000+ Steps), Night Skys Edge (5000+ Steps), Amity Meadow (2000+ Steps)