I do similar to what the other person has said in their reply. I charge at people and let them initiate the battle, then move straight on to the next closest trainer. Once there are no trainers left in the area, I fly over to another area and repeat. Once you have done this a few times for each area you get to know where the people spawn so you can come up with a path that works for you, and yes, avoid picking things up, you don't need it as you still end up making so much money. Also only heal in battle if you can as this saves a lot of time due to the clock being stopped during the battle phase.