Gold is more useful than you can possibly think.

[Mastertrek]

Do not underestimate the gold in any game where you can level up equipment by fusing weaker ones in it. (that works for most Kemco games but I'm talking about this game.

First of  all, Gold is useful to get consumables at main game (although you won't use consumables much, it's better to be prepared for anything. 

Second, Gold is another way (possibly the fastest way if you can get gold quickly) to get Maid Coins at Forgotten Garden (but you won't even get to that 22m Gold by normal means). 

Last but the most important for people who want to get all achievements available for the game. Gold is the best source for weapon leveling up. Not only there's a fast and steady way to farm Gold but also for every 99,999,999 Gold you can get one weapon level upgrade by +149/150 in very little time! 

https://www.rpginsanity.com/forum/fernz ... arm-guide/

For weapons leveling use the Weapon shop in Forgotten Garden. Buy all equipment for 88000g for a single person and level up the best current weapon over and over. This is way better than weapon drop hunting.