As to what people told me, get familiar with your character (whichever it may be) before buying potions. Once you die, it's permanent, so you don't want to waste pots with no experience.
When you get potions, they drop from in a place known as "God Lands", which can be found at the center of the map. When dungeons spawn (the little portals) if you complete them, you have a chance of getting a nice drop, but only higher level creature dungeons drop decent stuff, not like the forest or pirate portals.
Pretty much all I know about this game. GL
