Each game has 18 island groups.
Each game has four gym leaders.

Fight Lawrence Geraldin III on Mandarin Island So.?

~West~
New Island
Tarroco Island
Hamlin Island
Pummelo Island
-Gym leader: Drake
Kumquat Island
-Gym leader: Luana
Shamouti Island
a deserted island (1)
Millsweet Island
Mandarin Island No.
Mikan Island
-Gym leader: Cissy
Sunburst Island
Tangelo Island
Valencia Island
Pinkan Island
a deserted island (3)
Fairchild Island
Trovita Island
-Gym leader: Rudy
Mandarin Island So.

~East~
New Island
Hamlin Island
Kumquat Island
-Gym leader: Luana
Butwal Island
Ascorbia Island
Shamouti Island
Cleopatra Island
Navel Island
-Gym leader: Danny
a deserted island (2)
Kinnow Island
The 7 Grapefruit Islands
a deserted island (3)
Golden Island
Moro Island
-"Gym" leader: Misty 
--on vacation
Murcott island
a deserted island (4)
Mandarin Island So.
Trovita Island
-Gym leader: Rudy

~Other Info~
Shamouti Island is the home to the legendary birds, the Fire, Lightning, and Ice islands
with Moltres, Zapdos, and Articuno respectively. Lugia lives in the water under these islands,
and governs the other three legendary birds. He comes to settle their disputes.