Azshara can be amazing for dreamfoil farming in classic wow. It has lower level mobs than the alternative zones, and in addition, there usually is a lot less competition in this zone. You can either alternate between north and south, or you can focus on one side and leave the other one to other farmers, if there are any. If you have the Mining Profession, Azshara can also be good for Mithril and a little bit of Thorium farming at the same time as gathering the Dreamfoil.
As you can see on the map below, in Un’Goro Crater, you will just make circuits around the central volcano. You can alternate between the large and the small one, as there is more Dreamfoil in the south-east. You can also pick up a bunch on Golden Sansam and other herbs in this zone. If you have Mining, it can be worth it to go around the very outer edge, next to the mountains, to get a decent amount of Thorium, Mithril and Mountain Silversage, although there is very little Dreamfoil that far out. Be careful in this zone though! There are elite dinos roaming around, and there are more players in this zone in general.
Farming Dreamfoil in The Plaguelands
The Eastern and Western Plaguelands can also be great for Dreamfoil farming, while you can also pick up a lot of Plaguebloom there, which only grows in these two zones and Felwood. I won’t provide a route for classic dreamfoil farming in the Plaguelands, since the Dreamfoil is very evenly spread across the zone. If you are going to farm here, it may be worth it to pick up Mining or Skinning, too. The Plaguelands are great for combining gathering professions.