As you should probably know, every Pokemon on your team is fire type, so they tend to share weaknesses such as rock. Therefore, a lot of your teambuilding should prioritize covering those weaknesses.
Charizard: This is pretty much the only Pokemon I'd suggest you keep. The rest of them all share too many weaknesses and in general don't do much for the team. Replace sitrus berry with charizardite Y. Give it 4 Def/252 SpA/252 Spe Timid. Replace crunch and dragon pulse with solar beam and focus blast.
This is what I suggest replacing the rest of your team with.
Heatran @ Shuca Berry
Ability: Flash Fire
EVs: 252 HP / 4 SpA / 252 Spe
Timid nature
-Toxic
-Taunt
-Lava Plume
-Flash Cannon
The EV spread allows it to outspeed important bug Pokemon. Taunt delays things like hazards and healing. Lava plume has a good chance of burning the target. Flash cannon can help defeat rock Pokemon.
Victini @ Choice Scarf
Ability: Victory Star
EVs: 4 HP / 252 Atk / 252 Spe
Timid nature
-U-turn
-V-create
-Zen Headbutt
-Fusion Bolt
This is a good revenge killer and wallbreaker. U-turn lets you maintain momentum and not get choice locked. Fusion bolt is weakness coverage. This also happens to be the best Pokemon in monotype that uses two moves whose names contain hyphens.
Volcarona @ Life Orb
Ability: Flame Body
EVs: 4 Def / 252 SpA / 252 Spe
Timid nature
-Quiver Dance
-Flamethrower
-Bug Buzz
-Giga Drain
The idea is to use quiver dance to boost speed and special attack and then start sweeping. Giga drain covers water and rock and heals the user.
Infernape @ Life Orb
Ability: Blaze
EVs: 4 HP / 252 Atk / 252 Spe
Jolly nature
-Flare Blitz
-Close Combat
-Gunk Shot
-Stone Edge
It's an all-out attacker with two STAB attacks and two coverage attacks.
Torkoal @ Heat Rock
Ability: Drought
EVs: 252 HP / 4 Def / 252 SpD
Calm nature
-Stealth Rock
-Rapid Spin
-Yawn
-Flamethrower
This is several supports mashed into one Pokemon. It's weather support (which buffs fire attacks and nerfs water attacks), hazard support, hazard removal support, and it puts opponents to sleep. (I don't know a good name for this)
