Pokécharms

Personally, I kinda felt like they were the same difficulty. I very, very rarely struggle with gym leaders in Pokemon games, but in both Black/White and Black 2/White 2, I usually had trouble with at least 3 of the gym leaders.

Hm, I think I only properly struggled with the dragon one because... dragon.
And, probably the bug one too but that was just a poor team for it.

Usually Elesa, Clay, and Drayden are the ones I struggle with. Though it's a bit annoying that I struggle with them so much, I can't really complain much because at least they are actual challenges.

Oh.
Elesa.
I forgot how much I suffered against her Zebstrika.

Clay I don't think was that difficult for me, I think the problem I had was navigating the gym...

Her Zebstrika was an absolute nightmare, and so was Clay's Excadrill. I literally had 3 Pokemon that were higher leveled than both of them, with my 4th Pokemon being almost the same level as their Pokemon, and I STILL lost several times. :|

Yeaah, I think I used my starter to beat Clay pretty easily. I don't see much, other than not being able to hit it super-effectively, that would've made the Excadrill so bad...

But I definitely lost at least once or twice to that annoying as heck Zebstrika like seriously I always run from any and all wild Zebstrika I face even though I've beaten the game already and am far higher-levelled than they are-!

He's easier if I choose Oshawott as my starter, or on the very rare occasion Snivy, until he somehow miraculously manages a critical hit. It's even more painful if you pick Tepig, which is who I chose last time I restarted Black.

Yeah, I usually run from them too. Even if I need the EXP, I absolutely refuse to battle one unless I have to just because of Elesa's Zebstrika. XD Her Emolga is really annoying too

Mm, yeah true.
Not sure which other starter to pick for White 2, now that I think about it...

Hmm, maybe you could try using Pokemon that you've never used before, or don't use often, and depending on the types of them, you could choose a starter that's not gonna have the same type as any of them? That's personally what I like to do. I've played through all the Pokemon games I own quite a few times, and that's one of the ways I found to make the play throughs more interesting.

Maybe, maybe...
I'm thinking Oshawott.