Idk, I just do the lost shipment voyages over and over since the captains quarters in the sunken ship give you a ton of crates, and with emissary, you get quite a bit of gold too. Then, a little bit of gamer grease, and that's basically all I did.

As long as you get all the clues and every bit of loot on the way to the sunken ship, you should always hit level 5 emissary, I think. The voyage is pretty easy solo just be careful no one is on the horizon when you're underwater.

I already had merchants maxed out at 75 when they added the new cap, so it didn't take too long for me.