Selling mats from EX trials seems to do well for some folks.
Look at supply/demand on MB for your world and see what folks want that is high in demand but low in supply; typically prices will be decent and sell well.
Barding, glams, housing stuff, and quest items that folks need sell well too.

Though, take that info as you will, I'm not *the* best at making gil. Just advice I guess, even if it was just a little tiny bit helpful.