Don't bother, waste of time ressource and money unless  you are ready for it.

You will have bunch of useless sailors until 100+ that will consume slots such as armament or support sailors.

Optimisation sailors will need a first crew set or more. It means you will have to probably do 2-3 kaiser grind over just to hit that first step.

Then you will need to invest another time, money to get many vets.

If you want an answer in $ it is about 400 to 800$ just to get a high ammount of vets during the x3 conversion.

That is without taking in consideration the premium account to fasten the leveling.

An average of 2 month to pull the crew to 120 and since it is an equivalent of 2-3 kaiser grind, that would probably take 6 months for an average user to get that far. Constantly active (playing actively)

Because there's no answer to your question. Not enough details.

Your example given is still not precise enough.

Edit: Like number of times willing to invest, number of vets, etc.

your question was incomplete, so there is no answer.