Herblore

To acquire herbs you'll have to farm them or get them as loot. Non-ironmen however can purchase clean Guam and Irit Leafs at the Farming zone via the skilling tele tab. Speak to the Farmer.

Other ways to acquire herbs are Crystal Chest, Theatre of Blood, and Resource Crates. Zulrah, Callisto, Venenatis, and Vet'ion also drop herbs good for Sara Brews, Super Restores.
Any account type can purchase potion secondaries along with your vials of water from Bob Barter(Herbs) in the hut at ::skill.
He can also turn your clean herbs into Unf potions to save you time. To do this have in your inventory GP, noted clean herbs, noted vials of water, and use your herbs on him.
Being able to buy Clean Irit leafs and Eye of Newt (Super Attack Potion), or Ground Unicorn Dust (Super Anti Poison), or Magic Roots (Antidote++) makes it a prefered method to train the skill.