Mt. Moon and Cerulean City!
In Mt. Moon, you can catch:
Zubat Before you enter Mt. Moon, be sure to have a few escape ropes on hand. When you enter, beat every trainer you can possibly find. This is necessary for experience. If you've found the exit by now, good for you! Use it! If you haven't, use the map below to help you! The most north western staircase has the exit.
Once you defeat Team Rocket and exit mt.moon safely with one of the fossils, make your way to Cerulean city!
When you arrive at cerulean city, I suggest that you store the fossil you got from mt.moon in Ash's pc for safekeeping.
Now, after you heal your pokemon, go to the bridge north of the city. Prepare to face your rival! After you beat them all, you get a nugget(which can be sold for $5,000). Go west to the nearest forest where you can catch abra and oddish. Then go east from the top of the bridge and go to Billy's house. Save Billy and as thanks, he'll give you a ticket to the St.Anne ship.
You may then go down to Cerulean gym.
The gym trainer here is misty who uses water pokemon. Before you enter her gym, make sure you have a plant, or electric pokemon at the top of your list. Misty uses a staryu and a starmie. I beat her with my pikachu and oddish.
If you beat misty, you get a cascaderbadge.
After you beat Misty, go through the house that the police officer is guarding. Go through the hole in the house and beat the team rocket member there. Then follow the path down to vermillion city. On your way, there is a house below Cerulean city. Go there (you can catch meowth or mankey in the forests above the house). You may leave a pokemon for him to take care of if you wish (he charges lots of money!).
Then, go to the nearest "subway tunnel" as i call it and go down to vermillion city.