There are a few locations, but you will want to use the ones in the dungeon underneath Edgeville. Start at Edgeville bank, run south past the lever and go down the ladder and into the dungeon. Run to the area where there is a fence and an entrance to the wilderness (do not worry about being in the wildy, it is only for 2 seconds). Right as you go through the gate and enter the wilderness you will IMMEDIATELY see one of those Dungeoneering resource-dungeon hatches on your right hand side. Click that (level 10 dung required). This will teleport you into a room with like 10-15 chaos druids, and a few different herb spawns, including ranarr weeds (5k each atm). Collect the herbs as fast as you can and then use your glory amulet to teleport back to the bank, then repeat. Filling up your inventory with herbs shouldn't take more than 2 or 3 minutes. This is an excellent way to make cash with extreme ease and very little requirements.
Also - as for your question about the wilderness worlds to try looting in, high-risk is obviously a good choice. But some other popular worlds are 2, 6, 18, 65 etc. Also, just about any of the low numbered worlds are usually pretty crowded too, so try those ones to start.
