Game Intro:
You start off talking to Professor Oak who will give you your starter pokemon for free (apparently he’s got da big bucks giving away a free rare pokemon like that), either Squirtle, Charmander, or Bulbasaur. Once you choose, the game will show you two Team Rocket members hypnotizing a pack of Rattata to attack Oak's Lab. Choose your game version, and suddenly, the Rattata a noise sounds as the Rattata break through the wall.

Lvl 1, Oak's Lab:
Wild Pokemon:
Rattata

Lvl 2, Route 1:
Wild Pokemon:
Pidgey
Rattata
Uncatchables:
Joey's Pidgey, final wave

Lvl 3, Route 2
good place to lvl up on
Wild Pokemon:
red=Weedle
blue=Catterpie
Rattata
Pidgey
Uncatchable:
Rattata, final wave


Lvl 4, Viridian Forest 1
Wild Pokemon:
Weedle, Kakuna
Catterpie, Metapod
Pikachu (hard to get)
Uncatchables:
3 Pikachus, final wave

Lvl 5, Pewter Gym
Wild Pokemon:
None
Uncatchables:
18 Geodudes
9 Sandshrews
2 Onyx

Lvl 6, Route 3
go place to lvl up on
Wild Pokemon:
Pidgey
Spearow
Mankey
Nidoran (Male and Female)
Jigglypuff

Lvl 7, Viridian Forest 2
Wild Pokemon:
Metapod, Butterfree
Kakuna, Beedrill
Paras
Pikachu

Lvl 8, Mount Moon 1
Wild:
Geodude
Zubat
Spearow
Rattata
Mankey
Clefairy
Uncatchable:
Many Geodude, each wave, 2 at the end

Lvl 9, Mount Moon 2
Wild:
Zubat
Oddish (if you started with Charmander and don’t have a grass/water type, catch it!)
Geodude
Growlithe (catch it!)

Lvl 10, Cerulean Gym
Wild Pokemon:
Weedle, Kakuna
Catterpie, Metapod
Oddish
Pidgey
Uncatchable:
Horsea, in beginning on left side, starts a wave
Shellder, in beginning on right side, starts a wave
Goldeen, in middle on both sides, starts a wave
Staryu, near end on left side, starts a wave
Starmie, near end on right side, starts a wave
Giant Staryu, 2nd to last wave, by itself, left side
Giant Starmie, last wave, by itself, right side

Lvl 11, Cerulean Gym 2
Uncatchable:
Kyogre.

lvl 12, Route 24
Uncatchable:
all Uncatchable

lvl 13, Route 5
good place to lvl up on
wild:
meowwh
vulpix
abar
pidgey
jigglypuff
bellsprout
poliwag
Uncatchable
poliwrath
victreebel
ninetales
perian

more level to come