Start as a rookie sailor on a boat as tiny as a canoe and use your smart pirate moves to buy, craft or "arrange" add-ons for your dream vessel. Replace necessary parts, attach equipment needed for rides, focus on speed or durability, choose your own style of ruling the seas!
Galleons are great, but you need a crew to run it. Visit towns and harbors along your way, have a pint or five and recruit a crew that will make you a real pirate!
Whether it's trading, looting or finding treasures, you need to collect and stack your goods somewhere. When you spot this perfect place on a beach or inside a cave, claim it and take care of infrastructure and buildings to make your company thrive.
...and a way to look for them. You can turn every rock upside down and check every inch of the sea bottom, but if time is a factor, try searching for other pirates, merchants and shady people who may know a few stories about hidden chests.
As it happens sometimes - a pirate won't make a living from the trade alone and needs to incorporate a bit more dynamic forms of getting the necessary resources. On the seas, you might meet other fellow ships that just carry too much goods not to loot them. Way more efficient than honestly earned money.
Become a pirate! Arr!