My suggestion:

Level Desynth for LTW/Weaver/GSM, farm t4 while SB'ing, desyth the drops, sell sol tome mats, sell materia, sell mats.

Once you have enough gil, then start gearing up with the new offhands and crafter armour/accessories, unlocking master books etc.

But you do need a ton of gil for 4* crafting and tbh I think if you aim is to make more gil that it costs you... your probably too late, unless you want to put in an insame amount of time.