Best Way to Make Gil

Keep an eye on what you're able to craft with every level and what the MB prices are. For example I think around level 40ish you can craft a barding with LTW, I sold a couple of these quickly at 100k. Also, gear crafted from the rare dungeon drops (Qarn in particular) sell pretty high, whereas the not-so-rare drop sells for a low price, and you may want some for yourself as well. You could also try just making extras of whatever you need and put that on the MB to see what sells.

With gathering there are certain things that sell really well, but other than Flax I can't remember what. It's been a while.