I am also very poor in the game (have been since day one), I went from 1.5 mil (the most I've ever had) to 170k - I really should just level every gatherer including the dreaded fishing.
Farm Suzaku (Hells Kier EX). I'm constantly broke in-game as well. But I listened to a friend and forced myself to fight Suzaku all day before housing. Never rolled great on a feather but I was able to trade totems for shields and desynth them eventually to get at least 2 feathers. They didn't sell the night before housing since people were saving their gil. But the day after, they got insta-bought and I have at least 2million sitting in retainers right now. It's not much compared to gillionaires, but it's a start.

So if you have the patience to tackle one fight over and over do that one or Shinryu EX.