To start Herblore you will need Grimy's you can obtain these by killing certain monsters or you can grow them by using Farming. To start gather some Grimy Guam's and click to clean them, this will help you start the skill because you need at least 3 Herblore to start making potions.
Next with Coins and Clean Grimy's in your inventory then Teleport to Herblore in Skilling Teleports.
Once there talk to Sanfew to access the ingredient shops 1 and 2
|Grimy spirit weed||35|
|Grimy dwarf weed||70|
Making Potions Edit
Click the "Herblore skill" in the Skills tab.
To the right of "level" click the "?" it will show you what Herb and the ingredient needed to make that potion.