Greetings,
At the GameGuide there is a very convenient list which shows all gatherables per level for both ET and AT, as well as their locations.
http://gameguide.na.aiononline.com/aion/GatheringUnfortunately, this list is largely incomplete. This is where Aion ZAM comes to the resque.
Essencetapping:
http://aion.zam.com/wiki/Essencetapping_%28Aion_Skill%29Scroll to the bottom of the page and select the level range that applies to you.
There, click on "places" and you will see all locations you can find the resource at.
Alternatively, if you don't mind the old AION maps, you can use the Aionproject as it has a complete collection on all gatherables per location:
http://www.aionproject.net/Aethertapping:
http://aion.zam.com/wiki/Aethertapping_%28Aion%29You only need to click the number under "Locations" that applies to you.
Your Aethertapping Hat will guide you from there.
AT 400-450: Taloc's Forest
AT 425-450: Skysling Canyon
AT 450-499: Conqueror's Ravine (under the bottom fort)
AT 499+ (Ancient Aethers): Kaisinel's Beacon
One final tip: Gather on the Fast-Track server where possible. This gives double EXP (for your level, not craft) and prevents being ganked by Asmos.