Re: New Gold
I don't know what pokemon you like, but this team works very well in-game (I've listed advantages against the E4).
Ampharos: (Can cover all of Will and part of Lance)
Magmar: (Can cover part of Will, part of Koga, and part of Karen)
Hidden Power [Grass]/Thunderpunch
Espeon: (Can cover part of Bruno, part of Karen, and Will if Shadow Ball is used.)
Feraligatr: (Can cover part of Bruno, part of Lance, and part of Karen).
Ancient Power/Slash (Ancient Power is going to take some breeding to get. If you want it, go for it. If you don't want to bother, go with Slash).
Dragonite: (Can cover part of Bruno, part of Lance, and part of Karen)
Machamp: (Can cover part of Karen and part of Lance)
Rock Slide/Return (Rock Slide is only available through the TMs in R/B/Y. If you can't trade back to then, go with Return. You'd have to trade back before Machamp/Machoke learned Cross Chop or Curse though).
That team'll cover all of the types in the E4.
This should give you a good idea of what types are helpful for the game, even if you decide not to use this team.