Man of Means
Accumulate 1,000,000 pieces of gold.

This trophy is not cumulative. You must hold all 1,000,000 Gold at once.

This trophy is best left until New Game++. In addition to the options listed below, first save your game on a separate save. Next, sell every raw material in your inventory, this should rack up a few hundred thousand. An extra thing to note is that if you have the DLC, you can obtain 50,000 Gold after completing the missions each time. Thanks to CookieMcCrumble for the information and primalcarnage for the repetition confirmation.

Thanks to CookieMcCrumble for the information.

White Moonflower: The most tedious and luck-filled way to earn a lot of gold. Doing so involves manipulating the PS3 clock several times. For full details on how to obtain the White Moonflower see Obtaining White Moonflower

Fishing: Once you have completed the quest, The Fisherman's Gambit - Part 7, you will be able to catch Royal Fish with relative ease, which can be sold for 4,000G. Royal Fish can be caught with Earthworms at the Eastern Road Lake, with each Earthworm costing 10G.

Junk Heap B2 Run: In the Junk Heap level B2, there is a room in the far northern area filled with crates. In each crate there is a chance to obtain Amber, Fluorite or Damascus Steel, raw materials that can be sold for 3K+. Using the elevator to reach another level will make the crates respawn, watch out for the holes!