In the beginning of the movie, Gene first met Huey, Dewey, Louie, and Webby in the kitchen, then first met Scrooge McDuck in the boys' room.
When Dijon finds Gene in the lamp, he rubs it and he came out so Gene decided to call Dijon his master.
In the end of the movie, he was turned into a real boy and play Cops and Robbers with Huey, Dewey, and Louie.
He might become a member of the Shell Louge Squad, but with that position already being filled by Dijon, it's very unlikely. what also prevents this is that he becames a real boy at the end of the film, also undones that, but, should Gene somehow still retain his powers, it may be possable, and besides, Djon is set to join in Spongebob, Simba, and Friends meet bambi anyway, so it's nice to have an intermetit character till then.