Yep, afterall I am the only one that has a fic from the Orange Islands as of now. Here are the islands and gym leaders:
Valencia Island- Where Professor Ivy's lab is
Mikan Island- First Gym. Leader: Sissy, Pokemon: Blastoise, Seadra. Badge: Coral Eye Badge
Naval Island- Second Gym. Leader: Danny, Pokemon: Geodude, Nidoqueen, Scyther, Machoke, and Electrode(I think), Badge: Sea Ruby Badge
Trovita Island- Third Gym. Leader: Rudy, Pokemon: Ninetails, Executor, Starmie, Electabuzz. Badge: Spike Shell Badge
Kumquat Island- Fourth Gym. Leader: Luana, Pokemon: Marowak, Alakazam. Badge: Jade Star Badge
Pummelo Island- All-Mighty Gym. Leader: Drake, Pokemon: Onix, Gengar, Ditto, Venusaur, Electabuzz, Dragonite. Badge: The Orange Island Trophy
Hope thats what you needed. Thats pretty much all the info I have. Good luck with the fic!