Enter the Tree of Mana.
Talk to Pokiehl and work on climbing the tree. It's pretty hard to get lost in this land because there is really only one path that leads all the way to the top.
When you get to the Ruins-like area you need to find 4 sets of monsters and defeat them. The Ruins area is set up like a grid (3x3). After you defeat all 4 sets of beasts you will be taken to the Mana Goddess.
Get ready for a tough battle if you are playing this game through for the first time. I recommend leveling up as high as you possibly can before taking her on. The Diamond room on the 3rd level of the Bejeweled City has a Machine Golem that drops lots and lots of experience if you need to level quickly.
Good luck and have a happy end game. Don't forget to watch all of the credits and save your game at the very end. When you load this game+ save data you get to start all over again but you get to keep all of your items, workshops, pets, and orchard. You can also go to the library in your home and read the Forbidden Tome to change the difficulty of the game. Changing the difficulty increases the experience dropped and the chances of rare items being dropped. Now the game starts to get even more fun!!!
~~ The End