These routes are a good place to collect more Pokémon. Route #2 is full of Rattata, along with a specimen or two that are rarely found in this area. Remember to weaken a Pokémon in battle before using a Poké Ball on it, or else it will be able to break free. The first time you come through Route #2, head into Viridian Forest to continue your journey.
Spearows may not have a third stage of evolution like Pidgeys do, but they're a bit rarer, a bit stronger, and a lot cooler (and they get better attacks too, like Fury Peck and Drill Peck). Whichever you pick, definitely get at least one Bug-stomping Flyer if you have a Bulbasaur or Squirtle before you enter Viridian Forest.
Commonly found early on in Route #22, you'll find Mankeys' powerful fighting attacks to be very useful against Normal and Rock-type enemies especially because the first gym is rock type. You should get one if you have a Charmander because it has a hard time damaging the Rock-type Pokémon of the first gym. They learn their first Fighting-type technique, Low Kick, at Level 6, but he will not have any use in Viridian Forest because bug-type Pokémon have an advantage over fighting types.
You'll find your rival on route 22 after the first tall grass, but before the second. Your rival will only have two Pokémon, Pidgey and the starter, both at level 9. Pidgey can be easily defeated with a Thundershock (Pikachu can be found in Viridian Forest). Bulbasaur and Charmander can be beaten with Peck or Gust by Spearow or Pidgey; Squirtle can be beaten easily with Thundershock.
When you're done in Route #22, make your way back to Viridian City and exit through the north path to reach Route #2. Much of this route is inaccessible to you early on in the game, but that will change in time. For now, your only concern is reaching the entrance to Viridian Forest. Don't bother hunting for Caterpies or Weedles out here, they're more plentiful in the forest.
Caterpies aren't worth getting too excited about. Deciding which of the two bugs to collect comes down to whether you want an awesome Pokémon sooner, or later. If you'll willing to invest a lot of time with Caterpie, he will ultimately end up as a Bug and Flying-type Butterfree that will eventually learn powerful psychic attacks.
Weedle doesn't start out much differently than Caterpies. He's pretty weak when you get him, and evolving him into Kakuna doesn't make him much better. But his evolution continues at a lightning pace, and at level 10 you'll have an awesome (at least for the early part of the game) Beedrill.
Second visit
After you beat LT. Surge in Vermilion's Gym, you will be able to return to Route 2 through Diglett's Cave. You will get to the area which you couldn't get to in the beginning of the game. In the first house you see a kid who will want to trade an Abra for a Mr. Mime
Rattata
Mankey
Spearow
Psyduck
Slowpoke
Magikarp
Poliwag
Goldeen
Poliwhirl
Gyarados
Rival
Pidgey 9
Rival's Starter 9
144
Caterpie
Weedle
Abra
Mr. Mime
