If you're considering Desynthesis, a good enough guide to follow to increase your dLv is in the link I posted above.
For the purposes of the Mastercraft and Fieldcraft III Demimateria that we need, we have to aim for being able to desynth the iLv70 Artisan's tools, which are only available by trading items to an NPC in Mor Dhona. In 2.45, the number of items required to trade in to receive these tools was drastically reduced, making this thoroughly viable, if VERY time-consuming. However, you will need BSM, GSM or ARM dLv70+ to begin.
From a reasonably small dataset (of 90 so far - so please take with a pinch of salt), these desynths have been found to deliver the following results:
10% - 1x Mastercraft Demimateria
15% - 2x Mastercraft Demimateria
15% - 3x Mastercraft Demimateria
15% - 1x Fieldcraft Demimateria III
45% - (base materials dependent on desynth)
I'm going to discount the base materials gain here because although it's not insignificant gil, it does vary wildly depending on the tool desynthed.
So, on average, after desynthing 7x tools, you will have about 5x MD and 1x FD3. That's more than enough MD, so you can sell the two spare for 500k and buy the remaining 9x FD3s you need from the MB with 100k plus the value of the desynthed mats for your trouble.
This is considering dLv100. Desynthing the NPC-purchased 'Aged' items is a cheap way to get you nicely to dLv70-75 wherein you'll have a 60% chance to achieve the above result. That'd mean you'd need to get 12x tools for the same outcome. We have to judge now whether it's better to push dLv100 or take the breaks, based on the time and cost it takes to get one tool…
The tool you choose to desynth will depend on whether you've levelled desynth for BSM, GSM or ARM. BSM and GSM are the cheaper options due to lower number of hand-ins required for the CRP and WVR tools. I'm going to look at the GSM route here, but transplant your own choice into this procedure to get your own figures.
So I need 12x Artisan's Needles, for which I'll need to craft a total of 96x HQ Silver Brocade (two-star). The Silver Brocade itself is made from 21x shards, 2x Twinthread and 1x Silver Ingot. You'll want HQ materials to guarantee an HQ result (the NQ being essentially useless) and the cost of those on the MB is very high in comparison to the crafted cost.
The Silver Ingot HQ will cost 1,060 to craft apiece - 96x is 101,760gil and about 2hrs of your time.
The Twinthread HQ will cost 3,500 each - you should have no issue HQing this on-star synth from NQ materials. Of course, you will have to do it 192x, likely over the course of 4hrs. This may seem awful, but it's not so bad if you consider that there is an achievement for crafting 3,000 lv41-50 items and for crafting 3,000 HQ WVR items overall. It's a nice block towards those. Of course, if you don't give a crap about those achievements, then yes, this is heinous. Also, that's 672,000gil.
The 96x Silver Brocade craft with these items will take another two hours and cost an additional (80*21*96) 161,280gil in shards. I'd recommend making a full i30-34GSM set to spiritbind during this process and hopefully you can make some money back of Tier II materia
That leaves you on 8x hours of crafting and 935,000gil. If you don't have the ready cash, you can mitigate a large portion of it (537,600) by harvesting 384x Crawler Cocoons from the unspoiled nodes over at Little Solace (you should get 12-18 per hourly spawn), but this is just adding more time to the process. Getting help from your FC for a couple of days if possible is recommended! Also, being able to gather for 30secs once every 57mins during your working day can be a painless way of building this up.
In conclusion…
Mojo replied
575 weeks ago