To add about GC turn ins. If you turn in an item that is starred that day, you get double reward, both in company seals and in experience. If you turn in HQ item, you get double reward. And yes, if you turn in starred item in HQ, you get quadruple reward, that is, four times the usual. Also to note, regardless what class you are in when you do the GC turn in, the experience of those goes always to the respective class. So even if you turn in a row a weaver item and leatherworker item while having your main job on, you get experience to your weaver and leatherworker clsses respectively. Before level 35-40 I used to get a whole levels worth of experience from the turn ins per day since I adamantly turned in HQ items.

Another note of leveling, when you craft always use the skills to increase the quality. They increase the experience you get even if the result will not be HQ item. If you have increased the HQ chance to about 50% for example, even if you get normal quality result you get about 200% exp or so (can't recall the exact ration but seem to remember 300% is maximum) takes slightly more time but can cut ingredients needed to level a lot.