This achievement gives a combined amount between all 3 reclaimed resources (Magic/Rich/Weapons) and it does accumulate meaning you won't need to have a standing total of 1000 resources as long as you've acquired a life total of 1000 resources the achievement will pop.
Enemies around the River District will drop resources but I'd recommend doing the random vaults, they were dropping from 8 to 30 resources per run not including the ground drops and was averaging runs at 5mins, as mentioned on the other solution you'll find this so much easier if you grab some Alliance members or even community members from zone.
YOU CAN TRACK YOUR PROGRESS IN JOURNAL/ACHIEVEMENTS/GENERAL
Thanks, hope this helped!