Recommend
Gengar LV 80+ Timid/Modest
Item: Black Sludge
EV train: 252spatk|252spd|6hp
Move set: Thunderbolt, Shadow Ball/Icy Wind, Psychic
(Icy Wind teach by move tutor at Seafoam B4F by 5000$)
(Thunderbolt teach by tm buy at Vermillion City Gym by 3000$)
(Psychic teach by tm buy at Saffron City Gym by 3000$)
Gyarados LV80+ Adamant/Jolly
Item: Leftover
EV train: 252atk|252spd|6hp
Move set: Ice Fang, Dragon Dance, Cruch, Aqua Tail
And also don't forget take some backup items Revive x7, Hyper potion x15, Leppa Berry x10
The more level of your pokemon team, the less buying for backup items
E4 Team
• Lorelei • Gengar lead with using Thunderbolt for beat all team
• Bruno • Gengar lead with using Psychic for beat all team
• Agatha • Gengar lead with using Thunderbolt for Crobat and Pyschic for all
• Lance • Gengar lead with using Thunderbolt for Gyarados and Charizard, while Shadow ball/ Icy Wind for others. Also you can alternatively with Gyarados lead with using Cruch for Gyardos, Aqua tail for Charizard and Ice Fang for others
• Blue/Gary • Gyarados lead with using Dragon Dance 2-3 times at the beginning and then using Cruch for Alakazam and Mega Blastoise, Aqua Tail for Arcanine, and then Ice Fang for others