My daughter Pia introduced DragonVale to me last month and I easily got hooked. I have already reached Level 18 with 3 islands and lots of dragons! But aside from Rainbow Dragon, I still have to breed a Sun Dragon and Moon Dragon.
The easiest way to get these rare dragons is through Gems which you have to purchase. However, I wouldn't use my Google Money just to get these dragons. Haha! Never! Now, I wish I can find a really reliable DragonVale Breeding Guide.