Sewing is good to learn for all nationalities. Sewing's contribution to the community is to make good looking clothes, skill enhancing clothes and additional sails. Sewing is required for making certain ship parts, so is somehow necessary for shipwrights. Sewing, particularly making velvet in india (R13), is one of the most merchant fame/exp rich businesses. It does not require many skills, just sewing and textile trading, so it is very popular among non-merchant majored players. It was once very profitable too, but it has been weakened by the developer for game balance. But still it is a doable business.
Handicraft is good for all nationalities. Handicraft's contribution to the community is the furniture in the dorm, the figure head on your ship. They’re very durable. So the demand is not great. Fortunately handicraft is required for building a lot of ship parts and for alchemy, so it is a necessary skill for the alchemist and shipwrights.
Goldworks and silverworks are the only profitable business I can think about. They are perfect for the job of Money Trader. Making alcohol or sugar is ok for the early game. Later you would not do that. Gem cutting sounds compiling, but it not very efficient for the difficulty of getting those minerals. Strengthening boots is a famous handicraft business, the ultimate boots worth half billion for a pair. I never bought these since I am not a soldier.
Casting is mostly suitable for Spanish, and maybe for English and Dutch. Others have a way to make money from it too. Casting is very import for the community, because cannons do not wear so well. You may consume 20 cannons a day if you’re doing intense maritime practice. Cannon making is a moderately profitable business and is only convenient for the Spanish. Casting makes armour plate, armours, helmets, hand weapons, sterncastles…so it is useful for sure. Making firearm goods in India and southeastern Asia is a possible business, although not the most efficient.
Shipbuilding is divine because this game is all about ships. Better ships make huge difference. Shipbuilding is very simple and profitable (assuming the ticket bug will be fixed). The income of the shipwrights is mainly the tickets they get from the shipyard. Merchants deeply rely on these purchase orders. The downside of It is that it just takes very long. If you can reach R16+3 in 2 months, you are a demigod.
Most important things Storage makes are the contributes to PC and NPC pirates. Turn fish into ration is another practical use of it.