[Bozos of Bones]

You will see your first gold just before the Gates of Kryta mission. It will not be max damage, not even near it, but that is where most players pick up thier first(all 4 of my chars managed to get their first there). You can be extremely lucky with purples, I found a +5 Insightful on a purple staff in the jungle, and that was one very lucky drop.
So, to get things straight:
White and blue: from the start of the game
Purple: I got my first at Nolani. Purples will always have a mod.
Gold: Kryta onwards. Golds will always have two mods.
Max Damage: From Droknar's Forge and all the later areas.
Green: In Grenth's Footprint and Sorrow's Furnance, drops from bosses. They are max damage, max bonus mod and with two perfect mods. They are unmoddable and uncolorable.
If you don't know where something is, don't ask cause you'll get there eventually and you'll only want to cheat and run yourself there.