The most common gold coins in circulation are the American Eagle, the Gold Buffalo, the Australian Kangaroo, the Chinese Panda and the Canadian Maple Leaf. The Mexican Libertad and the South African Krugerrand are also pretty popular on a large-scale buying and purchasing market. Be prepared if you want to buy gold coins online with Bitcoin or with Litecoin because there are thousands of types of gold coins out there, but those few just stated are the most common that you will find.
Some gold coins are 99.99% purity including the Australian Kangaroo, but the American Eagle is only 91.67% gold, so make sure you know the purity before you buy gold coins with Bitcoin. Any way you go, you cannot go wrong with gold coins due to the value of the coins over time, whether you want to use them as an investment or just collect them.