only continue to power up #1, but unless you need the cp for gym placement, don't power up any of these until the gym rebalance.
for me, I brought the snorlax that have to lvl 30, then only have powered up the best iv ones as needed for gym placement (my highest IV is low 80s)
as far as it goes for power up the one very high or many at high: it all depends on your local gyms.
once again, the future gym rebalance could change everything. So it is better to have available candy in order to react to future changes.