The right time to buying the altcoins is the time when they just been created if you know that they will grow. Or wait for dips.
there are two types of buying altcoin first when it is offered in the ICO period you can bought it when there is a bonus it is better of course second one is that when there is a dip because when the ICO ends the price will drops because of the moment that the bounty hunters sell all their coins.