In DragonVale for the iPad, iPhone, and iPod Touch, you start the game with one island, and the rest have to be purchased as you gain levels and gold, since they each have an increasing cost.
Some can be purchased with gems as well, if you’re into that kind of thing.
Here are the Islands you can get in the game, when you unlock them, and how much they’ll cost you.
Starting Island – Unlocks at level 1, costs 50 gold
Second Island – Unlocks at 10, costs 75,000 gold
Third Island – Unlocks at level 16, costs 2,500,000 gold
Fourth Island – Unlocks at level 20, costs 10,000,000 gold
Fifth Island – Unlocks at level 25, costs 50,000,000 gold
Sixth Island – Unlocks at level 30, costs 100,000,000 gold
Gemstone Island – Unlocks at level 11, costs 400,000 gold
Epic Breeding Island – Unlocks at level 13, costs 125 gems
Epic Breeding Sanctuary – Unlocks at level 13, costs 225 gems (replaces Epic Breeding Island)