Gold or G is the standard currency in Chrono Trigger. In most RPGs, G (or similar abbreviation) stands for Gold. G is the accepted currency in most time periods, even in Prehistory and the Future, where it is called "shiny stone" or maybe questioned as money, respectively. The exception to this is in Prehistory where the Ioka Village Hut merchant accepts Petals, Fangs, Horns and Feathers in exchange for special weapons, armor, and headgear. Gold is accepted by most merchants in exchange for their goods. G is awarded by defeating certain enemies or found in chests.
Gold can be gotten in a variety of ways from defeating enemies, charming enemies items to equipping an accessory called Workman's Wallet to turn exp points into gold. Here's a list of places to farm money.
Early on in the game, over at the Site 16 area, the player can fight plant monsters Meat Eaters later called Flora Horrors to win ether's to sell for 750 Gold each, the player can make enough money to buy the expensive sword for Chrono called Demon Edge later called Zanmato at Medina Village for 65000G.
The player can go to the year 65,000,000 BC to fight the Nus for 3 of each Fang, Feather, Horn, Petal which can be traded for weapons and armor which can be sold for money.
The player can also have Ayla charm enemies for weapons and armor which can be sold for money.
The player can have Robo lead the party and fight robots on the conveyor belt in Geno Dome.
The maximum amount of Gold the party can have with them is 9,999,999.