THIS EXERPT IS TAKEN DIRECTLY FROM Hikari62's Shop/stamp/piggyback guide. http://www.gamefaqs.com/ps3/604158-tales-of-graces-f/faqs/64962#section25
Since selling earns you 1.1x towards the gald count that earns you stamps, I suggest using that to your advantage. Selling a +3 poignant (or fabulous) Dreamer's Flange will usually earn you 300k+ gald (actual amount depends on the level of the shards you use and whether the weapon has one or two effects. In my experience they have ranged from 270k to 570k). I'll explain how to do this. However, if you don't know the basics of dualizing weapons, please check the Equipment Dualizing Guide on the FAQ page.
IMPORTANT: See Useful Recipes/Books section to make this method more efficient.
Buy Rare Shotstaff at Gralesyde (complete stamp Lv7). Dualize with a High-Grade Crystal (Lump of Clay + Decaying Sword). Lump of Clay can be obtained from: Discovery in Region 66. Mixer - 22.2% production chance (more efficient than above). Decaying Sword can be obtained from: Enemy ??? (24% drop). There are three enemies named ???. The one I'm referring to is the floating black ball that can be found in field locations around the world near end-game. Eye of Wrath in World's Eye/Lambda's Cocoon (24% drop). Diamond Weapon in Ghardia Shaft (24% drop). Mixer - 6.1% production chance. The dualized Rare Shotstaff will become a Dreamer's Flange (Epochal). Dualize with a Stuffy shard to get Dreamer's Flange+1 (Stuffy). Temper and extract. Dualize with a Wicked shard to get Dreamer's Flange+2 (Magical). Temper and extract. Dualize with a Gallant shard to get Dreamer's Flange+3 (Poignant). Or dualize with a Sketchy (or Epochal) shard to get Dreamer's Flange+3 (Fabulous). Temper and sell. Sometimes dualizing a shard with the proper quality onto the weapon will not change the weapon's quality. I do not know exactly why this happens (it has something to do with the shard level I think), but it happens infrequently. Just find another shard and try again. Use the highest level shards you can (higher level shards allow the weapon to be sold for more gald). Level 3 or 4 at least. High level shards can be obtained at the following locations. Stuffy shards - Ghardia Shaft (Center), Zhonecage floor 4, 10 Wicked shards - Ghardia Shaft (Center/Depths), Zhonecage floor 1, 7 Gallant shards - Ghardia Shaft (Center/Depths), Zhonecage floor 2, 8 Sketchy shards - Ghardia Shaft (Base/Center), Zhonecage floor 4, 10 Epochal shards - Ghardia Shaft (Center), Zhonecage floor 6
There are a lot of ways to get a 200k item, but the more different you want to be the more knowledge you need of dualizing system, like with the inn requests if you don't care about the dualizing system, this is as step-by-step as it gets.
Be careful while extracting, by the way. One of the reasons you use something like an Isleberg or Dreamer's Flange is because it comes with a built-in ability, which means when you finally sell it it will have two abilities on it, which multiplies the price even more. If you extract and you see in the preview window that one of the abilities on the gem are increasing (orange), then you probably have an overlap ability- which means it'll extract BOTH the abilities on the Isleberg/Dreamer's, which is something you don't want. I've done this a couple times accidentally and had to sell my Dreamer's for a mere 290k instead of the 400k+ that I was shooting for. Well, if 200k+ is all you want then it shouldn't matter either way though.
Also, if you're like me and you find Ghardia Shaft to be bollocks and don't have Zhonecage yet, I find shard gathering at Bathus Citadel much easier for gallant/wicked/stuffy shards. I'm not sure why, but I had about the same droprate there, but with significantly less laser one-shots happening every once in a while. Your mileage may vary. Try it out if you want a change of scenery.