Where can I get money before the third gym?

I need to get money so I can train my Pokémon in my secret base to fight Perfectionist Taen. I don’t have enough for that incense that doubles your money, and I do have an Amulet Coin.

The amulet coin and the luck incense do the same, the effect doesn´t stack if you use more pokemons with both held items in a battle.

At that point in the game you should use the dexnav to fight trainers and get money, the elder Clint Eastwood has only an Electrode that can be defeated by any ground type, it gives $2400 or $4800 with the amulet coin.

The other option is Gentlema Dun who only has a Dunsparce, it gives $3600 or $7200 with the amulet coin as a reward, but is a tougher battle, all the pokemon trainers are at level 50.