How to get infinent money

Fighting and playing chace will get you enough berries

Another way is to Tackle lots of trees with Berries in them. Sometimes, you can find a Golden Berry, which is worth 100 Berries, while the Red Berries are 10 & the Green Berries are only worth 1. It's the easiest way to gain Berries, and you can Tackle each tree in every area as many times as you'd like. Simply enter an area, Tackle each Berry Tree 2-5 times in a row, exit the area, and enter it again to collect an infinite amount of Berries, while Battling & playing Chase on the side (the max amount of Berries is 9,999).

Battling Emboar and Samurott give you 300 berries each for every win. My tactic is to use razor shell 3 times for Emboar, and spam the dash combo on Samurott. With maxed dash combo on Snivy, and max razor shell on Oshawott, you should be able to finish each battle within 10-15 seconds.

Note: It will not let you battle Emboar or Samurott until post game I believe. I didn't figure out that he gave you this many berries until I battled all the final evolved starters, which were the final Pokemon I befriended in the game.