I'm just considering starting up FireRed again... I just can't look past using the version mascot but I don't want to end up having to struggle through the first two gyms with Charmander. Any tips please, or it looks like I'm not going to play this game at all!
If you want to run Charmander and not struggle through the first 2 gyms, here's how you can get through it:
Brock's Gym: There is one Pokémon in the first few routes that you can catch that will help you avoid beating Onix/Geodude with Metal Claw: Mankey. You can find him on route 22 and he learns Low Kick at level 6. I think once he's level 10 you should have no trouble beating him.
Misty's Gym: For her, there are a couple options:
Since you have Fire Red, you can find Oddish in the patches of grass after Nugget Bridge. It's definitely the best option, since it's pretty bulky, and I believe it has Absorb when you catch it. Should probably teach it Bullet Seed (found in Mt. Moon), since it will out-damage Absorb.
You can catch a Pikachu from the Viridian Forest if you have the patience to find one, and if high enough level, it outspeeds Staryu no problem. However, it doesn't learn Thunderbolt until level 26. It will be tough to survive stab water pulses.
You can also catch a Paras in Mt. Moon and teach it Bullet Seed. Problem with Paras is he can still get 2HKO by Starmie's Swift or Water Pulse.