The gold coins are easy to come by, and this will definitely unlock early on. For those of you who are unfamiliar, they are larger gold-colored coins worth 5 times as much as the normal coins.
There are three main ways to get these coins:
1. Inside Crates. When you bust open crates on your run, there's a chance that a lonesome gold coin will pop out.
2. During Fever Mode. Below your coin counter there is an orange meter that builds up as you hit the enemies. Once your meter is full, you enter fever mode and all the coins on your path turn gold for a short amount of time.
3. Take the High Road. After reaching 2nd evolution (expert), you can purchase the double jump skill for 1 skill point. You will occasionally see a hanging platform which you can double jump up to. Double jump on to that, then the following platform, and you will be on a multi-obstacle gold coin path.
I hope this helps. If there is any negative votes, or things I should add; please comment!