The crafting guide I posted before was more for money-saving, but if you have a couple 100K to 1M gil, it's really easy to crank out 5-10 levels daily:
-Under the levemete menu, go for the levequest that is out of the way (ex., a Gridania quest that has a drop-off in Mor Dhona, instead of being conveniently in Gridania's 2 drop-off points). It has more reward that requires only 1 item turn-in, double EXP if you turn in a HQ item.
-Set 2 favorite destinations so that you can bounce between the levemete and drop-off location.
-Gather up all your required material to be able to craft 15-18 HQ items (this is only for 5 levels, by then another 5 levels will require a different quest and ingredients.) If anything requires animal material (Boarhide, Beastkin blood, Piesteskin), just buy that stuff HQ from the market board. It's not worth the effort to farm and you will usually need that HQ stat. I had to do this with fleece, even though it took quite a chunk out of my cash.
-Drink crafting potions/meals for 3% EXP, buy them in 99 bulk at the shops, unless you're a high enough CUL to make HQ meals for more Bonus
-After gaining 5 levels, complete your next crafting mission and then repeat the grinding process for the new leves.
-When you hit lv 50 in a crafting/gathering job, always complete the lv 50 (last) mission. You want that iLv 50 tool and optional item.