the only Pokemon found before the first Gym are Patrat, Lillipup and Purrloin. It's like that the Trainers only use Pokemom caught in the area around them for some reason.
As Hikari10 had said, we can only find them in the first grass (First grass before the road 3).
We are forced to play with them, because it's hard to play only with grass or water pokemon until the road 3.
The Timburr and Roggenrola lines also get a special mention for being too commonly used by Trainers (mainly Hikers).
I mean, they really had a lack of diversity compared to previous games.
Timburr is the easiest fight type to find. (and the first with Sawk & Throh but they're a little harder to find that a Timburr) The other fight types aren't available before a "long time".
In my case, I pick my starter, I catch a Patrat (to help me during the first gym). After that, I put him in the pc.
After that, I stay only with my starter but when I come to Nacrene, I go catch a Sawk, If I dont find him, I take a Throh and if I'm not lucky, I take a Timburr.
If I don't have a water type as starter, I take a Tympole. [I had one in my current game, but I'm sad, because, he can't learn "waterfall" (?? I'm speaking about the hm to climb the waterfall) So, I took a Frillish].
So, When I come on road 4 (before to go in the third gym), I search a Darumaka (to beat Burgh).
If you follow me, at this time, I've
Starter (Grass) + Water + Fight + Fire
or Starter (Water) + Fight + Fire
or Starter (Fire) + Water + Fight
Once I beat burgh I go near the Relic Castle to find a Maractus (Even if I've a Starter Grass, I replace him by Maractus) And once I come to the road 6 I can replace Maractus by Foongus (If I'm not satisfied of Maractus).
Before, Once I came to Icirrus, I caught a Cryogonal. But now (Thanks to Cyclone) I know that we can find Vanillite before.
So, You have as a team
Maractus (Foongus) + Water + Fight + Fire + Ice
But have we really the choice of our pokemons ? Knowing that we are limited to 150 (included their evolutions).
For example, if I look for one water type which can learn Surf, Waterfall and Dive. I am limited to:
Oshawott
Panpour
Basculin
Tirtouga
Frillish
Alomomola
And their evolutions if they have.
So we are limited and people (like me) don't want to have 2 water types in the team.
So, we are forced to choose in these... and we naturally have all the "same" pokemon.
Without forgetting the pokemons which serve only to show "all the power" of the others.
It's the same with all the types. They are only :
6 races of Dragon (evolutions not included BUT the three legendary included).
I don't know exactly where they plan to go with the pokemon black / white. But I hope that it will not be about a stagnant series which we shall incorporate into the other generations but rather of a parallel series which will develops itself with new regions and especially new pokemons.