Are there any trainers somewhere in Diamond which I can easily defeat and spam the VS Seeker on? I badly need to grind for the Pokémon League. Provided that this is a Nuzlocke, I would also like to earn more cash to buy enough healing items before I take on the Elite Four.
Well, I suppose I will answer this.
As sumwun stated, use the VS seeker on route 223 to train your Pokémon’s levels, and rematch the old couple near the Pokémon Mansion with the VS seeker with a Pokémon holding the Amulet Coin to get money for potions. I recommend getting your team all to about 60 or so to beat Cynthia. If you caught Dialga, give it a Shuca Berry and you can OHKO Cynthia’s garchomp with Roar of Time. You can get a Shuca Berry from Pastoria City. Also, beware of the lucario of hers. For me it was worse than her garchomp