okay, , lots of help needed, so here we go.
1. You need atleast 6 pokemon on your team.
2. Your pokemon need to atleast be in the mid 50's- mid 60's. A good place to train would be One Island
3. The basic movesets for your pokemon should be this.
Gyarados
Surf
Icebeam
Dragon Dance
Hidden Power Flying (filler, but hp flying is the best choice)
Golem (trade someone for to evolve him)
1. Explosion
2. Rock Throw -- Rock blast preferably
3. Double Edge
4. Earthquake
Venusaur
1. Leech Seed
2. Sleep Powder
3. Toxic (or sludge bomb, but i prefer toxic)
4. Giga Drain
Obviously the annoyer Venusaur, but is an incredible staller so you can heal your other pokemon.
Pidgeot
1. Mirror Move
2. Aerial Ace
3. Feather Dance
4. Whirlwind (psuedo hazer)
For the rest of your team, i would suggest-
Electabuzz (if you play fire red)
1. Thunderbolt
2. Substitute
3. Focus Punch
4. Ice punch (for the ground and rock types that will kill him)
OR
Raichu (if you play leaf green)
1. Thunder Bolt
2. Substitute
3. Focus Punch
4. Light Screen
Arcanine (fire red)
1. Extreme Speed
2. Flamethrower
3. Bite/Crunch (breed)
4. Roar/ Hidden Power ground
Magmar (leaf green option 1)
1. Flamethrower
2. Thunder punch
3. Confuse Ray
4. Psychic/ Protect
Ninetails (leaf green option 2)
1. Flamethrower
2. Confuse Ray
3. Willow Wisp
4. Double Team
The latter is probably the most annoying moveset i came up with in a long time.
Those are the pokemon i would suggest you use. Here's the thing though, Agatha is going to be hard for you, unless you switch out one of your pokemon for a psychic one. In which case, i would take out Golem, and put in a psychic type.
Alakazam (psychic type option 1)
1. Psychic
2. Calm Mind
3. Recover
4. Shadow Ball
basic set
Hypno (psychic option 2)
1. Psychic
2. Calm Mind
3. Hypnosis/ Thunder Wave
4. Rest/ Wish
there, now remember that all of the elite four have move sets to counter their weeknesses, (Lorelei's Lapras knows earthquake, Bruno's fighting pokemon know rock tomb, Agatha's pokemon know shadow ball and psychic, and Lance's pokemon know earthquake, thunder, and dragon moves. And gary, well, good luck with him.)
Hope that helps a little bit, and remember, the movesets should be balanced, so only have one type of move per pokemon. And mine are just samples, so be creative. Good luck with the elite 4.