I use the vs. seeker to find trainers that want to battle. If you haven't beaten the Elite 4 yet I'd raise your pokemon more than you need to for them. I did that and it took FOREVER to beat them. I'd get my butt kicked by Lance or my rival, Idiot.
Bring plenty of revives, max potions, and anything else you can get to boost your endurance. For money, I go to 5 island with the amulet coin and battle the people at resort gorgeous. But before I got there, I battled the gamers east of Vermilion. Maybe there are better people who give more money but that's where I went when I needed cash. Double battles are pretty easy to win and I think it's a good way to get experience. Good luck with raising your team!