IMO stay about 25 or more above what he sayd above to go to new area. i went:

• UC 1-70
  
• Silverspine 70-90 ish
  
• hillsbrad 90-100
  
• wetland 100-170
  

• made a quick pass through Hillsbrad to get to 103. went to arathi. and it was not my lvl so i went back to hillsbrad
  
• wetlands was mostly kingsblood and liferoot for me, was a few briarthorn that i picked up tho. >>alot of mageroyal at thelgen rock<<
  
• I must say wetlands was amazing after 125, lvld very fast in no time flat
  

will edit when i get more info on my experiance.
+ Gatherer mod IMO is a must for LVLing and farming matts at 70

FYI this is all after 2.3 if that has any thing to do with herb