I keep trying to breed the Amber dragon using the combo of Evergreen and Quake, as seen on the website. I want to know if there is any other combination or if this is the right one, because I've been trying since the day this dragon came out.
Evergreen and Quake are the only combo, however, this combo can breed a further 17 dragons so there are many failures, one of the worst being the Crystal dragon which, using the breeding island, results in a 20 hour breeding time (or 20 gems to speed up). So far I have managed to get 2 Amber Dragons (used Gems to speed up some failures) but am now on my 2nd consecutive Crystal dragon. Just keep trying
All gemstone dragons have a single correct breeding pair. However, they have an extremely low chance of being bred.
You are correct that the Amber dragon's combo is Quake and Evergreen - this is not only the (statistically) fastest combo, it is the one and only combo, period.
The only things known to have an effect on breeding chance is having your dragons at higher levels (15+), and having the Epic Breeding Island. Most other "get dragons quick!!" tips don't have any real effect.