Board Thread:Dragon City Questions & Answers/@comment-33686200-20171114003006/@comment-2601:201:282:34B0:C7:5DD4:F693:2B3B-20200107184459

Grid Coins are only used while Oni Island is the current event island. Event islands hover just to the right of your first island, opposite Midarian's Tower.

TL;DR - Generating Gold: Best is collecting from a level 1 Terra habitat that reaches full 500 gold capacity every 10 minutes. Every habitat at full capacity will give you 6 Grid Coins each, and then has a 10 minute cooldown.

I've found habitats generating gold pay 1 Grid Coin for each 20% capacity, and an extra one for full capacity, with a cooldown of 10 minutes on that habitat after you've collected Grid Coins from it. That's why you'll get 3 Grid Coins when the gold bars icon first appears over a habitat (because it just generated 60% of it's capacity), and once that icon becomes opaque you'll get 6 Coins. One of the quickest ways to do that is with a level 1 Terra habitat that generates it's max of 500 gold every 10 minutes, or with a dragon with an income rate of about 50/min. Is there a 2-element dragon that takes about 10 minutes to breed and hatch? ;D

-Cypher16e