Easy training
Start your game and get your Pokemon that you started with to at least lv.17 (make sure it's not over lv.21) and catch some Pokemon but only train your starter once it is at a satisfying lv.start to train your second Pokemon to the same level and then your third and after that all of your others (I didn't do this in my emerald but it worked on fire red so good luck and happy training) :P
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