In this new feature you have a little island as a base. you can collect wood, gold and gems from surrounding islands. You can raid enemy bases and be raided. You have access to all the ships you have unlocked in Carpentry and Tailor. Ships start at lv 1 with a very low capacity so:
1) Use your ship(s) to collect wood until all your ships are around level 8 at least and only upgrade during a New World event.
2) Do not keep too much wood at once, use as much as possible or enemies might raid you. If you get rewards from events with wood in them its better to keep them safe in the chest till the event comes along.
3) When your ships are high enough focus on collecting gems whenever possible, if no gems are nearby then wood to improve your ships.
4) In case of battle against an enemy, note that your ships stats depends on your own in game stats so it is hard to know who has the best ships. Further more quantity of ships is more important than quality.
5) If you do not attack your neigbours there is a good chance they will leave you alone.
6) The Arabian Night ship costs 1 million gold in the Tailor cabin or 8 tokens if you have them, buy it it will be useful.
7) If your ships are damaged you have to pay gold for repairs, stats of said ships will be reduces accordingly to damage taken.
8) If your home is raided you will loose half of your wood stock but no gems nor gold.
9) There are 3 different level of the Leviathan boss, level 1 is rather easy even with one ship and low BR. LV2 is already a lot harder and unless your BR is already quite high i would recommend sending 6 ships on it or avoid it. Lv 3 is obviously even harder and you may attack with 6 high level ships and good BR to ensure victory.
10) Hydra boss: Do not try to fight him without 6 boats ! You will lose too much gold from the reparation. My advice is to focus on the rest of New World till you feel strong enough to beat them, damage is cumulative so it is a good idea to attack with friends to speed up the process only the one dealing the last blow gets an additional reward.