I just watch certain things. For one you gotta have some Gil or start small, then you set a bottom and top line on ten or so stackable items, a line you buy and sell at. If you watch a day or two and use the history you get a pretty good idea where those lines should be, sometimes it's much longer timeline than that and those are your moneymakers. I only let that out though because I own portions of my market, I'll drop price to bait an undercut then buy you out and relocate your Gil into my bank. I make 20 grand in around 20 minutes if I use my retainers, it's not instant but it works