Importance of picking desynthesis skills?

So, I've been debating getting really into desynthesis for one major reason: I can't decide what to pick. On the one hand, there's the standard of CUL, GSM, LTW for big fish desynthesis, fieldcraft III, mastercraft, and primal demimateria. But there's also relic items now, plus desynthesizing things like dungeon drops to consider as supplemental income.

At the moment, I've started on culinarian, and I'm considering GSM and ALC for the other two. Not branching out TOO much from the standard, but at least I get one relic item that's not completely flooded. Still, I can't help but be a little hesitant about picking a wrong skill and wasting a ton of time and gil.

Which skills are the best skills to have keeps changing from patch to patch so I'd just go for whatever's easiest for you to level.

GSM is just way too good. It's one of the easier ones to level and being able to produce both Mastercraft and FC3s is incredibly useful.

LTW is not as necessary depending on the price of FC3s on your server. On mine it tends to be around the price of how many shoes it would take to get a similar amount of FC3 unless you are really lucky.