virtualrock- I typically play a smuggler *almost* like I play a pirate, in regards to attacking other ships. With the exception being that I only attack other smugglers to take their gold and sell it for myself. Always look for transportation jobs for your faction- these are much safer early game, and pay almost as well. Make sure you keep a few nations in the areas you frequent happy with you- you can't sell goods if everyone hates you!
+1 En1gma I tend to play a less violent smuggler, but stealing gold sound like a good idea!
Keep an eye on surpluses and shortages too. Selling contraband at a shortage will greatly increase your profits. Store surpluses you don't need on an island to sell later. The Smuggler has a special ability that gives them a chance to generate free journals when selling contraband. Negotiation sets the max number of journals you can earn.
ncaoa agreed on the violent part- I almost never attack the factions, just trade guilds that I decide upon at the start of the game- if I play Ruesland, I go for Hansa and Octopon exclusively. I want to be the only one smuggling sometimes tho, so some games I attack all smugglers on sight- very lucrative!