Earton crossroads sign:
Earton Water fountain:
Underneath the fountain in Horseshoe village (fountain closest to General Store)
Ice Isle on the left to Sandcastle Moat #18
The entrance to Nilan's walnut maze Jungle Isle on (the second torch)
On the veg patch in Molten Meadows, Lava Isle
Most Ancient Statues have treasures somewhere around them on Jungle Isle
You can also dig on the red Xs that you find (pirate treasure)
Quests will probably make you the most money. To earn even more money put your money in the bank and you will earn interest.
Selling diamond necklaces on Rock Isle (see Isle Directions)
What you need for diamond necklaces:
Gold chain - gold ore
Diamond - Rock Store
3 gold ore - Rock Store
You can make the necklaces on Cat Isle.
Picking up stuff and selling it, stuff like gems, logs, berries, food, etc.