MiltankRancher already covered Infernape and Luxray but I'd recommend Bronzong, Starraptor, Gyarados, and Garchomp for your remaining team slots. You can find Starly or Staravia pretty early in the game and it does have its uses against Gardenia and Maylene so raising it shouldn't be too much of an issue. Same deal with Bronzor too. You should be able to get the Old Rod pretty early in the game too but personally I'd wait until you got Surf and the Good Rod so you can catch a Gyarados and already have it decent off the bat, especially if you can teach it Dragon Dance and Waterfall as well not to mention Ice Fang will be crucial as well. Gible can be found in Wayward Cave near Eternia City but it evolves into Garchomp around level 48 but despite that it will be a very useful team member by that time especially if you teach it Earthquake.
Here's a few sample movesets to use.
Starraptor - Fly, Close Combat, Take Down/Return, Brave Bird
Gyarados - Dragon Dance, Waterfall, Ice Fang, Strength/Bite
Bronzong - Gyro Ball, Hypnosis/Stealth Rock, Reflect, Light Screen
Garchomp - Earthquake, Dragon Claw, Fire Fang, Swords Dance
Hope that helps.