Okay here are the tips and tricks:

Crafting: daily GC turn ins HQ, (chose a base mat that is used in many synths) quick synth in mass or put a short macro together that does a few quality steps then finishes the synth, ixal dailies till 50, leves, moogle dailies 50-60, collectables.

Gathering: daily GC turn ins HQ, grind gather (check what mats you need a lot of, ex. Walnut or check mb for what sells well ex. Flax), leves, unlock every node (bonus exp).

FC buffs help, food buffs always, if you have extra GC seals Manuals. The class quests also give out exp and have good stories. Always play the MB if you can make or gather something easy and make a profit do it. Lastly when your gear SBs convert it, the materia will be useful later even some level 1s.