Primarily I really enjoyed the stories from all of the crafting and gathering classes. I'd personally recommend leveling them just for that alone, though that is a significant time investment so its up to you. I'm not really crafting or gathering much right now as i'm on break playing the Witcher trilogy lol... the market is a complete mess atm too though and I've already far exceeded my original goal of stockpiling enough gil to buy a mansion before the next expansion releases a new housing area. Really, if you're going to do a lot of crafting you're going to want to do it because its fun for you. The gil will come naturally along with it. I also enjoy that I can craft a full set of i380 gear for any of my other secondary classes without much fuss.