Torterra: Torterra, Luxray, Floatzel, Lucario, Rapidash, Gengar/Alakazam
Torterra: Wood-hammer, Earthquake, Crunch, Rock-climb
Wood-hammer for STAB as you can not get Seed-bomb until after the E-4 (Note you need a heart scale to remember Wood-hammer). Earthquake he learns by level up as soon as he becomes a Torterra(lvl.32), this provides excellent STAB. Crunch gives very important coverage against Lucian, who is the hardest of the E-4, which will prove very useful. Rock-climb is an HM but it can also confuse the target.
Luxray: Crunch, Thunder-fang/Thunderbolt, Iron-tail, Strength
You get Shinx very early in the game so a Luxray is easy to get. He has a very limited move pool, however he is still a valuable asset to the team thanks to his huge Attack stat. Crunch is for Lucian. Thunder-fang is his BEST PHYSICAL STAB(remember this is before Wild-charge), so Thunderbolt is an option but if you choose to get Gengar then it is better on him. Iron-tail is for some coverage. Strength is HM and neutral coverage. (Note: If you actually are willing to take the time to breed him then Fire/Ice-fang are options).
Floatzel: Surf, Ice-beam/Punch, Waterfall, Focus-blast/Brick break
Buizel comes in fast so this will be easy. I know TWO WATER MOVES but this is ingame and two HMs is more than worth it. Ice-beam/Ice-punch is IMPORTANT this is the guy who is going to take out your worst enemy CYTHIA'S GARCHOMP Floatzel should outspeed him if you level it up enough and then POW dead Dragon..Shark...Thing... Ice-beam is easier to get as you do not need to collect shards for a while to get it. Surf and Waterfall are STAB Hms. Focus-blast for power, Brick-break for Coverage.
Lucario: Aura-sphere, Dragon-pulse, Dark-pulse/Psychic, Extreme-speed
He takes a bit longer to get as you do not get him until Iron-island, however; he is very useful. Aura-sphere is STAB and very useful for getting the occasional Double team Pokemon. Dragon-pulse is coverage(NOTE: I do not expect Lucario to outspeed Garchomp to use this unless you level him up a lot and with EVs or trade a choice-scarf to him). Dark-pulse or Psychic, Psychic if you choose Alakazam, Dark-pulse if you choose Gengar. Extreme-speed is good for finishing off things, like Alakazam or if Floatzel does not completely kill Garchomp.
Rapidash: Flare-blitz, Bounce, Mega-horn, Poison-jab
This guy is pretty much your ONLY option for a fire type unless you choose Infernape. He comes in the game very fast. Flare-blitz is very strong stab. The rest is coverage. This is your main guy for defeating the Ice gym and the Bug E-4.
Gengar/Alakazam: Shadow-ball, Psychic, Thunderbolt/Shock-wave, Focus-blast
Gengar gets T-bolt Alakazam gets Shock-wave. Both are useful special sweepers that you can catch early in the game. It is up to you.
However you could switch Lucario/Gengar/Alakazam out for a Flying type, most likely Staraptor.
Staraptor: Close-combat, Fly, U-turn, Steel-wing
Also you may want an HM slave to carry the weak HMs like Rock-smash and Cut. Bibarel and Lopunny are decent options.
Will give more info later
If you Choose Chimchar as your starter you should replace Rapidash for Roserade. If you choose Piplup as your starter replace Floatzel for Roserade.
Infernape: Close-combat, Earthquake, Flamethrower/Flare-blitz, and Shadow-claw
Empoleon: Ice-beam, Surf, Waterfall, and Earthquake
Roserade: Magical-leaf/Giga-drain, Sludge-bomb, Shadow-ball(If you choose Gengar)/Stun-spore, and Cut