Stop scaring the guy with this talk of needing 15 pokes and Iv training on all of them.
A well balanced team is more valuable than any of those. Then if a gym is uber tough, you just need to make a simple substitution of one poke to counter the field, two in the worst case.
Strategy, supporter mons, sweepers, tanks. A good balance of these will save you time in training 15 perfect pokes.