Restore Your HP at the Save Points !
1. Near a save point, press A
2. Save your game.
3. Exit the save screen and access to the in-game menu by "Y".
4. Go to System Page and choose "Quit" (This will bring you back to the Game Main Menu)
5. Load your saved game again. The health / mana of your entire party is recovered.
6. You can also Restore your HP by exiting back to the world map !! So, before you rest at the inn, be sure to double check your HP !!
Thanks to sleepyhomme from GameFAQs for the awesome tip !

Easy 50.000 G at The Gamblers Hideout (Gohtza City)

First, you need at least 10.000 G and access to the Gamblers Hideout at the Low Town area 10th Floor in Gohtza City. Talk to the guy here and he'll ask you to "invest" your money. Choose to Invest 1000 G and he'll give you a signed loan paper. Exit the screen, and re-enter it and he'll ask you for more money. Give him another 1000 G and head out from the room and re-enter again. Repeat this step 8 more times until you receieved 10 Loans Paper from him in total. Re-Enter the screen again one more time and he'll give you 50.000 G back in return !! Sweet !

Pipot and the Seeds

If you're wondering what are you suppose to do with all those Seeds, you need to give them to Pipots (which can be found inside the pots on some areas, example, there's one at Grand Staff Construction Base). Here's the items you can get from it.

20 Seeds - Adamantis Sword, Adaman Ring
40 Seeds - Earth Charm
60 Seeds - Power Angle
80 Seeds - Gigan Brooch
99 Seeds - Pipot Charm