This all depends on the server, again.
Hey guys, while leveling my herbalisme in tanaris, I noticed that when I got to the auction house purple lotus and fireblooms were really worth the time. I also saw the Mithril Bars were alot of gold too.
Purple Lotus = 30g/stack
Firebloom = 10g/stack
Mithrill Bar = 50-60g/stack
For people that herb and mine, it's really good money for a low level place. It also depends on how fast you can farm them. You might also find some Truesilver Bars, and those are worth ALOT but you probably won't get a stack but good enough anyway.
Also: If not already, get the AddON Gatherer and Routes. Install both of them and when in-game, config Routes.
For the herbalismes/miners out there that don't know how to track both at the same time, simple you just need a macro. Place it on your action bar.
/castsequence Find Herbs, Find Minerals
Hit the macro every few seconds to toggle between the two.
Well, this was another of my guides... I really hope this works for you! Any questions/comments or any opinions about this goes in the comments section below! Thank you.