If one way of being successful is Battle every trainer, then you know the same can be said by talking to all characters in every town and building. By doing this, you will actually be given loads of TMs, Healing Items, Berries and more along your journey for absolutely nothing! You'll also find a given trainer or two that will want to trade with you or give you a Gift Pokemon for free! Also don't forget to check trash cans for additional free items!