Maybe you should have posted this in General Discussion.
But I will answer anyway you get money by killing pokemon and looting what they drop (i.e. Fishing will net you Water Gems, Water Pendent)
After killing certain pokemon you get different loot depending on what the pokemon is (i.e. Rattata drops apple bite, Diglett drops small stones)
Then you can sell most any pokemon except for any of the pokemon you can get on Beginner Island (Magikarp, Rattata, Pidgey, Oddish, Paras, Caterpie, Weedle).
