The top left of this website has ship tree and sailor tree information you can refer to to see the ships crew sizes and how to get those sailors.
Also, the forum has a tips and tactics sections which (if you click view old data in the top right of the forum) can show alot of useful information, however most links within forum posts no longer work.
Your crew setup should be 2 gunners to be your main gunners, 2 gunners to be your AA gunners, and then a range of engineers and repairers, to improve your speed and repair ability. There is a third support, the restorer, however they are rendered useless at higher levels so having even 1 is not recommended. You should also level a pilot to be a scout, you turn a sailor into special forces at lvl 12 and then into a rookie pilot at 25, they can specialise further at higher levels but they can only fly scouts if they stay rookies their entire careers. All this and ofc, your bridge officer.
Thats some brief information to answer your immediate questions, I recommend you check the tips and tactics section aswell as reading useful information on the very important www.trainworld.us
Good luck, comrade.