Step-by-step: Here be pirate gold!
Start the task by finalising the design of the coin itself. Wikimedia Commons is a great resource to study what old coins looked like. The benefit of designing a coin from the top- down view is that you can easily use Photoshop’s tools to both copy and mirror parts, and rotate details using the Elliptical Marquee Tool, without having to take perspective into consideration.
Once you’re happy with your coin’s look, duplicate it a few times, rotate it around and put it in perspective using the Distort tool. Of course, your coin will look flat when you do this, so each time you’ve put a coin in perspective don’t forget to make it thick by painting the border. Think about the ground shadows too, which will help to make your coins feel grounded.
Now merge all the coins together (Ctrl+E) and click Image> Adjustments >Gradient Map. Create a new gradient and carefully pick colours so that you gradually build your values from bright yellow, to warm saturated oranges, to dark browns. Look at your coins while you’re doing this, and move the colour sliders in the Gradient editor to keep your values in check.
Make your gold coins shine by adding a new layer on top, changing its blending mode to Color Dodge and using a warm orange to boost the highlights in random spots. It helps to go outside the borders of your coins layer – that way the shine will really make the coins pop. Not all coins will be facing the light directly, so some coins can be darker than others.