Ideally, your first squad on your whaleship won't die. So, you should really put your best units there. Alpinia and Maple for example, should always be on your first squad, regardless of the color of the whale, unless you can form a full squad of 6* girls of the right type. Reason being, Alpinia can tank quite well, and also hits quite hard. Maple improves Alpinia's trigger rate, meaning Alpinia will get a better chance to steal HP through her special attack, further improving her "tankiness". So try to keep those two together, at least for now, until you can form specialized squads (trigger squads, debuff squads, dodge squads, etcetera). And even then, matching up Alpinia with +Skill Rate girls is always beneficial.

Remember to apply trainable abilities to all girls on your whale, especially those on the first few teams. ATK up on the first turn is a good start, since it's useful for every girl. But, Alpinia for example, benefits even more from the Recovery Boost ability.
Also, put AOE girls at the front of your squads, it improves the chance for the squads to take out an entire batch of pests.