Using the Sunset Colister Map, you can enter the Sunset Colister located in the Red lotus Palace Main Street. There are 3 ways to get gold in the sunset colister, selling the sealed skill jades on TH, selling the Goddess equipments to the NPC and finally getting Gold Goblin.
The Goddess equipments sells for ~152 gold each and the Gold Goblins drops ~2000 gold
Doing special missions(Plunder, Coop, Alliance, Target, Counterattack, Treasure, Mining, Front Breakthrough) grants you 305g for completing them. It is recommended to run on multiple sub accounts to maximize the daily 3600 FTG given to every character. Doing this also allows you to sell those special missions to other players such as Coop, Alliance, Plunder, and Guild missions for additional gold.
Example: (The prices for missions varies)
Another way of farming gold through mission board is by Tomb Hunting. To get the tomb invader it is recommended that you have general mission for that specific dungeon to increase the chance of its appearence. The tomb invader drops a random skill jade and the fragments dropped could be used to craft sealed skill jades to sell.
The GGC drop rate is currently 0.3% but will be increased to 1.8% in the future patch. In a normal run it should grant you 6000+ gold