I'M BACK! Sorry, lost computer access for a while plus got sick, etc., busy with work-BLAH! Anyway, sorry to not be here b/c I'd meant what I said about helping. I just was gone too long...
It seems as if you've gotten through by relying on Charizard and Pidgey/Pidgeotto(why is it not a Pidgeot? Level 36 he can evolve)and the 2 others eventually to get you through the game-and it's a stategy that will work, but you miss out on alot! You must catch as many different Pokemon as possible, as far as I'm concerned-others may disagree. I think you should have a couple or more of each that you like, as well as 1 of each you can get your hands on!! Any WILD Pokemon is up for grabs-but not those who are owned by other trainers. You had to have caught the mankey and pidgey and dragonaire/dragonite, so you must know how, right? Just when you battle them wild, instead of knocking them out, just put them to sleep(a few moves do that, but not all pokes can learn them but those like Jigglypuff, Clefairy, Drowzee, Abra will get or have them if you catch one.) Until then just catch a few low level ones that are easy by lowering their health some or using a status condition and just throw pokeballs at them-it's really very easy once you get the hang of it. You find them all over, use the fishing rods in water to get water types, walk through grassy areas, and catch rather than beat them in battle. Go back to safari zone and catch a bunch in there. You can only have 6 in your party-but the PC has plenty of storage for others, just go get them out and store others there to use the different ones.
Let me know if this helps at all as a start, and ask me anything you don't get. I'll be back more often from now on, and will keep checking back. I knew you were a Scorp! Been doing astrology for 20 years....so I know once you catch some and check out the cool things they can do, and will learn, you'll want to catch each one to see if you like them or not-check out their stats, special abilities, and move descriptions. You might like Psychic types(Abra/Kadabra/Alakadam) and Fighting types(Machop/Machoke/Machamp), plus the stronger, more impressive ones like Dragonite, but you have to try them out to know. A guide that tells you where they can be found and what moves they get or you can teach them(all those TM's you got do have a purpose!), like a Prima or Nintendo Guide(Gamestop, Barnes & Noble)they're a big help.
Well, that's a start and I'll wait for another post to write more. Ask me something, whatever, but let me know if I'm helping. I'm guessing once your party had some strength, you just worked well with them, and didn't bother to catch others b/c you didn't need them. If so, this should help, and just go back through the game and catch the ones in each area, and there you go-off to getting a huge collection. Don't underestimate the basic pokeball, most of the common pokemon you can catch with it, if they're on the red and asleep or paralyzed, it will be easy most of the time. I'm hoping you didn't kill all the special ones like Articuno, Moltres, Zapodos, Mewtwo, b/c they're a one shot deal. SAVE B/F TRYING TO CATCH THESE!!!! If you mess up and kill 'em, just turn off the game or hit A + B + SEL + START to reset. (This works for all of them of course!)
OH-go to Celedon Mansion, in the back way to get a free EEVEE(MORE ON THIS LATER). Go to Saffron Fighting Dojo and beat all trainers, he'll give you a choice between 2 fighting pokes. Bring Old Amber to Scientist in Cinnabar to get Aerodactyl. There's 3 right there!
Happy hunting!! Just go out and catch, catch, catch! Fill that pokedex!
P.S. What are the levels of your party and the moves they have? The highest they get is LV 100, but you may know that by now. You may not be able to find all of the different types of balls described above, but that's ok. Use what you can buy in the pokemarts(Regular, Great,Ultra-use the better ones if you have trouble or are going after a higher level or special pokemon)but the descriptions given are great. Also, check out the terrific walkthroughs for LeafGreen and FireRed right here at SC! They're great as well-and free-DIG IT! I LOVE SUPERCHEATS. It's great here...
I got all the Pokemon a person could dream of, and still working on more. If you need to know the truth, seek it out here, as I am obsessed with answering all the questions I can as best I can. I can verify Event Pokemon, too! My collection keeps growing!