Route 19

Route 19 (should be a bit bigger than the one in the game, like a long rocky beach where you get through in order to get to the ruins of the city, which are partially blocked to you by a cuttable tree and therefore you are forced to move to route 15 from there) -

 

Lvl avg - 4

Water: Tentacool (40), Wingull (20), Magikarp (40)

Grass/Or sand maybe? - Meowth(50), Wingull(30) Venonant(20)