Those random golden chests that you see floating by can be opened by either watching an advertisement or paying 10 gems. They get mighty tempting later on when structures begin to cost astronomical amounts of wood.
Since there is not really anything else to spend gems on, you can go ahead and quick open these golden chests to get a nice chunk of wood if you do not want to wait.
There is one thing to this though – it is better to start opening golden chests during the later parts of chapter than it is early on. The reason being is that the amount of wood inside the golden chests actually scales to how far you are in the current chapter.
So, naturally a golden chest at the beginning of a chapter may hold up to around 5,000 wood, whereas the later chests can have up to around 50,000 wood! Since the gem cost never changes, it is best to hold on for the moment.