I'll catch a Pidgey, it certainly will help you with the grass, bug pkmns on the way to goldenrod, then I'll catch a hard pkmn or I'll level my pkms like around lv 22 for the third gym, of course yOu can get a machop on the big store on goldenrod, very well, personally 'll cATCH a nidoran male and transform it into a nidorino :) Also before you get to goldenrod you might consider catching a ditto, that way you'll have eggs!!!
ANY WAY REMEMBER: It's not about quantity but quality, don't catch to many pkmn!!!