Ahem, this will be long, as you should know, battling Pokemon gives you EVs, you can get 510 EV in total but only up to 255 EVs in each stat, every 4 EVs is one stat, which u will see at lv. 100. as for Vitamins like Protein and Zinc, THEY GIVE YOU 10 EVs in one stat, you might be thinking that your life is now perfect, you can waste money on a Pokmon rather than training it, expecially due to the undella bay in Black & White. However, you are wrong. Vitamins can only give you up to 100 EVs in one stat (that would be 10x$9800=$98000 for 10 vitamins) but the 100 EVs to get u started is actully Very Helpful.