Let's see...last I recall, I was able to meet at least seven other Gym Leaders, though I am aware of there being more than that I just haven't had the chance to meet yet. [Like Drayden, for example. Iris didn't seem to be keen on him, though.] And naturally, they all vary when it comes to what type of flavor they have as a trainer.
It was Lenora, Burgh, Elesa, Clay, Skyla, Brycen, and Roxie that Ash and I met with on our journey. Respectively, they had normal, bug, electric, ground, flying, ice, and poison-type Pokemon that they liked to use in their gym battles. They were all very interesting people to get a chance to taste the skills of, even if I was only observing most of Ash's battles with them back when he was collecting the badges. [...] Other than my brothers, the only Gym Leader I've had a battle with personally so far is with Skyla and her flying-type Pokemon.
[written, 20th July]
It was Lenora, Burgh, Elesa, Clay, Skyla, Brycen, and Roxie that Ash and I met with on our journey. Respectively, they had normal, bug, electric, ground, flying, ice, and poison-type Pokemon that they liked to use in their gym battles. They were all very interesting people to get a chance to taste the skills of, even if I was only observing most of Ash's battles with them back when he was collecting the badges. [...] Other than my brothers, the only Gym Leader I've had a battle with personally so far is with Skyla and her flying-type Pokemon.