Best Overall Location To Earn A Ton Of Money
If you're looking to get a lot of money battle, much like where the place is to gain the most overall experience, look no further than Elite Four. Unlike the rest of the Trainers found throughout the game, only the Elite Four can be challenged as much as you'd like. And since their Pokemon are some of the highest leveled in the game, you will gain all the more money than other, basic trainers.
You would be able to earn double the amount of Poke Dollars if the Amulet Coin had been invented in the First Generation of Pokemon, but, sadly, it wasn't created until the Second Generation. Again, you have to do things the old fashion way in these games.