Cyndaquil and Tododile are the best starters so you should get them over Chikorita. Cydaquil is a Fire type which is rare early on and works better if you want the Red Gyarados but Tododile has a better level up movepool. Kangaskan is available in the first Pokewalker course and the Pokewalker has a 50% chance to choose it. You have a 50% chance to find one after you walk 3000 steps, which isn't much if you take it to work/school etc. You have a good chance of getting one with Scrappy and since it has almost as high Atk as Feraligatr and Fake Out, you shouldn't have any problems killing things. Geodude is the best Rock-type in the game, IMO, since it also gets Magnitude and Earthquake by level up as well as Selfdestruct and Explosion. It also works well against the half of the gyms and you can Paralyze and Explode on a tough opponent. Crobat is one of the best Flying-types and although Zubat is rather bad at first, it can easily take down Sprout Tower (except for Hoothoots) and once it learns Bite at Lv. 13 and Wing Attack at Lv. 17, it becomes a much better. Kenya is the Spearow that you get from the guard right above Goldenrod that you're supposed to give to the sleepy guy next to Violet City (he only gives you Rest so don't worry about keeping Kenya). It starts out at Lv. 20 and already has Pursuit and Aerial Ace. Mareep is the best Electric-type since it evolves fairly early and they're really aren't many good Electrics. It also learns Thunder Wave early which helps out slow Pokemon like Geodude. The choice for the last slot is mostly dependant on which starter you chose so you don't have two Fire/Water types. The Red Gyarados can be obtained at the Lake of Rage at Lv. 30 while your Pokemon should be in their mid 20's and the trainers will be using Pokemon in their low 20's. It will start out with Dragon Rage which will easily 2HKO all opponents Pokemon for a while. Ho-oh is obtained late but is definately the best Fire-type. It starts out at Lv. 45 while you're Pokemon won't be level at Lv. 40 unless you grinded with them. Arcanine is obtained earlier so it's a good alternative and you can evolve Growlithe right when you get it by getting a Fire Stone from the Pokeathlon.
Start the game and either get a Cyndaquil or Tododile. Use the Pokewalker to get a Lv. 8 Kangaskan. Head up to Route 46 to catch a Geodude. Head to Dark Cave to get a Zubat (if you want one). Capture a Mareep on below Violet City. Head to Sprout Tower and get Rock Smash. Level up Geodude to Lv. 11 to get Rock Throw and/or level up Mareep to Lv. 10 to get Thundershock and defeat Falkner. Head to Azalea. Defeat Bugsy with Quilava, Geodude, and possibly Flaafy. Teach Quilava/whatever Cut (or Headbutt), it'll apriciate a better Normal attack than Quick Attack. I think the Soothe Bell is in Ilex Forrest so you should get it and equip it to Zubat. Make sure to take Zubat on atleast on walk in the Pokewalker and give it a haircut every day you're in Goldenrod. Get Fire Blast from the Department Store for Quilava/Growlithe and Thunder for Flaafy, you can get Return for Kangaskan as well if it's Sunday. Crocanaw/Gyarados could possibly use Blizzard but they'll get Ice Fang anyway. Teach Geodude Rock Smash. Get Kenya. Defeat Whitney's Clefairy with whatever and defeat her Miltank with Geodude's Rock Smash. The Defense drops will ensure it doesn't get to stall with Milk Drink. Participate in the Bug Catching Contest and get a Fire Stone for Growlithe from the Pokeathlon on Tuesday. Get Dig in the National Park and teach it to something. Catch a Growlithe, evolve it, and teach it Fire Blast. Head to Burned Tower to do all that stuff and head to the Dance Studio to get Surf. If you've raised your Zubat well, it should evolve into a Golbat at Lv. 22 and a Crobat at Lv. 23. Defeat Morty with Crobat/Kenya and Kangaskan since it will have Bite and Scrappy. Head out of Ecruteak to the right and a Hiker will give you Strength; teach it to Kangaskan. Head to the Lake of Rage to capture Gyarados; teach it Surf. At this point you can either head to Olivine City or stay and fight Team Rocket/Pryce. Evolve Geodude into Graveller and Golem when you can. Head up the Lighthouse and learn of the situation. head to Cianwood City and defeat Chuck with Crobat/Kenya and Flaafy/Crocanaw/Gyarados for Poliwrath. You can use Selfdestruct on his Primeape provided Double Team doesn't make it miss. Get Fly and teach it to Crobat/Kenya. Fly to Olivine and defeat Jasmine's Magnemites with Graveller and defeat her Steelix with Quilava/Crocanaw/Arcanin/Gyarados, just watch out for Rock Throw. Fly to Mahogany and defeat Pryce with Flaafy and your Fire and Water-types. Defeat Team Rocket in Goldenrod. Fly back to Mahogeny and head to Blackthorn. Let Flaafy learn Discharge before evolving it. Make sure Gyarados/Feraligatr have Ice Fang/Blizzard. Defeat Clair's Gyarados and Kingdra with Ampharos and defeat her Dragonair with Gyarados/Feraligatr. You can always use Selfdestruct on her Kingdra if you Paralyzed it with Discharge/Thunder Wave. Get the Extremespeed Dratini. Capture Ho-oh. Head to the Pokemon League. Get Earthquake in Victory Road and teach it to something. I don't really remember what the Elite Four/Kanto Gym Leaders have but it should be pretty intuitive to defeat them.
