So far we know the first Gym Leader specialises in Bug-type Pokémon. The second, third, and fourth will most likely specialise in Rock-types, Electric-types, and Fighting-types, respectively.
I would think having a Grass-type starter would make the first Gym Leader difficult to beat. Fennekin might have trouble with a Rock-type, however. Grass-type Chespin should do fine against Rock-types and Electric-types, but like I said it will have some trouble at the first Gym. If it evolves into a Dark-type before the fourth Gym it might have a challenge there too.
Froakie will have problems with the Electric-type Pokémon from the third Gym, but should do fine in the other Gyms.
zappy800, lol I knew someone would ask. Well lists such as my list on my "about me" section. But more importantly, my lists of Pokemon. I have hundreds of lists where I divide Pokemon into categories. Some are type categories. Examples include: Grass-types, Basic Grass-types, Dual-type Grass-types, Baby Grass-types etc. So I also have a Fairy list now