I do a mixture of things; writs every day as people have already mentioned (currently doing on 14 characters). I sell things I acquire from playing (whether it's from the writ rewards or exploration o
I don't like farming, I rather spend money to buy mats, so my gold has to come from normal gameplay. Of course when I get drops which I already own I sell it.
Bonus chances of faction motifs which always sell decently. Not the best way to do it, but I was farming the motifs myself and it was nice getting all the extra gold from the ornate drops.