Gathering Guide

Mining level 300 - 2 achievements, 'Miner' title, Angel Halo head piece.
Essence Gathering level 300 - 2 Achievements, 'Energizer' title, Faerie Globe head piece.
Plant Gathering level 300 - 2 achievements, 'Harvester' title, Sunflower Band head piece.
All skills level 300 - 1 achievement, 'Gathering Master' title, increased inventory space (1 full row).

Tier 1: (Gathering Levels 0-101)
Kynemetal Ore - In Arcadia, the top left section, top left of the map
Sun Essence - Same as Above
Verdra Fibers - Gather throughout the Island of Dawn experience and Fey Forest.

Tier 2: (Gathering Levels 101-151)
Linmetal Ore - in Chebika, there is a small section called "The Vast Sands", they are found in high abundance here.
Wind Essence - Just above the Linmetal area is another area full of Linmetal but also quite a few Wind Essence piles.
Sylva Fibers - In Arcadia, Celestial Hills, near the bottom left outpost there is a small lake with Sylva Fibers everywhere

Tier 3: (Gathering Levels 151-201)
Normetal Ore - In Cutthroat Harbor, Mistmoor Island, to the right of the vindicator basecamp is a road leading towards what appears to be a shore.
Star Essence - Throughout Cutthroat harbor and Pora Elinu, no specific farming location yet.
Shetla Fibers - In Cutthroat Harbor, Mistmoor Island, near grim coast at the bottom, there is a small intersection on the map, inside there is a few enemies that block gates, within is currently the only good spot I could find. Some users are saying that there are tons of Shetla fibers found around the Colossal Ruins which is North of Tulufan.

Tier 4: (Gathering Levels 201-251)
Shadmetal Ore - if you move North on the map from the BAM area for Toira fibers, you will find even more BAMs (fangspawn this time) and deposits of Shadmetal ore. Careful because unlike the rocky BAMs, fangspawn move and when they move that brings you closer to getting aggro'd.
Essence of Ice - When traveling towards Serpentis Isle (the gate on the right of Castanica), there will be a section where there is a single giant crab and a bunch of turtles on your left. There is nothing but Ice Essence here and since the turtles do not aggro this place is perfect. Just switch channels when you start running low.
Toira Fibers - After moving through Castanica north, follow the road to the left until you get to the rocky BAMs, there's quite a few there with barely any aggroing mobs (except the BAMs but they won't bother you unless you get within breathing distance)

Tier 5: (Gathering Levels 251 - 300)
Xermetal Ore - Once you get to Kaiator, enemies tower above in level so this is dangerous. These are found absolutely nowhere in Val Tirkai. In Sylvanoloth to the South of Kaiator, there is a section called "Amena Outla" to the bottom right of Amena Outla is a circle on the road filled with a new type of Fimbralisk BAM, the ores can be found here.
Lightning Essence - Lorcada, Plains of the Damned, near the camp Firebase Audacity. There are a total of 5 lightning essence nodes to gather from. These are spread apart but the trick is to gather from the nodes close by and then change channels and gather from there. One of the nodes is sometimes covered by an aggroing enemy so I highly suggest you ignore that one.
Luria Fibers - Once you get to Kaiator, head North-West to Val Tirkai, connecting the 2 sections is a cave to the far top left of the map of Tirkai Forest. Inside that cave are absolutely no mobs but at least 10 plants all within feet of each other. These are also found in small abundance in Thrall Hold also inside Val Tirkai but they have an incredibly fast respawn time so you do not have to run around finding a lot of nodes, just find at least 2 or 3 next to each other. I went to the bottom left of Thrall Hold towards Skyfields, found 3 nodes and farmed them, everytime I finished all 3 nodes, the first one I picked respawned almost as soon as I finished gathering the plant or as I was gathering the plant.