Order of Islands

In case you were wondering, the order of the islands for Poptropica is... 

Early Poptropica

Shark Tooth Island

Time Tangled Island

24 Carrot Island

Super Power Island

Spy Island

Nabooti Island

Big Nate Island

Astro Knights Island

Counterfeit island

Reality TV Island

Mythology Island

Skullduggery Island

Steamworks Island

Great Pumpkin Island

Cryptids Island

Wild West Island

Wimpy Wonderland

Red Dragon Island

Shrink Ray Island

Mystery Train Island

Game Show Island

Ghost Story Island

SOS Island

Vampire's Curse Island

Twisted Thicket

Poptropolis Games

Wimpy Boardwalk

Lunar Colony

Super Villain

Charlie and the Chocolate Factory

Zomberry

Night Watch

Back Lot

Virus Hunter

More to come...

Of course, this list is not easiest to hardest. However, I recommend if you are new to Poptropica you start with Early Poptropica, which most people would call the easiest island.