Tons of Crafting Mats

[Solarra]

Am kinda focusing on the main story quest line AND ranking up in the GC

In that case I recommend doing the GC Provisioning and Supply 'quests'. Every day you can turn items in to the GC in exchange for seals and xp. Handing in HQ will double your reward. If the item has a star by it, the reward is already double what it would be normally and again, handing in HQ items will double the reward that's shown.
The list changes daily at 9pm server time. It's not like a regular quest, if you have the item in your bag and the list resets you won't be able to hand it in.