It can be a very slow process and may not prove worth the time

Salarin

Confined to a small room, Salarin the Twisted is an evil druid who is located in the Yanille Agility Dungeon. One will need level 67 Agility to gain access to his hideout. Salarin is immune to all forms of attack—melee, Ranged, Magic—except strike spells. Salarin is found amongst Chaos druids, who are also good for collecting herbs while waiting for him to spawn. Every now and then, Salarin will drop a Sinister key, which opens the chest in the room just past the entrance with the balancing ledge. Whenever you open the chest, you will receive: 1 Torstol, 2 Harralander, 3 Ranarr, 1 Kwuarm, 1 Irit, and 1 Avantoe. Although this may seem like a good method, it can be a very slow process and may not prove worth the time.

Scroll of Cleansing

After obtaining the Scroll of Cleansing as a Dungeoneering reward there will be a 1 in 8 chance that you will make potions twice as fast, and a 1 in 10 chance that you will save the secondary ingredient of a mixed potion so if you are a fan of Dungeoneering this is a good way to save on time and costs.

Equipment

Herblore gloves, when worn, increase the drop rate of the specific herb your glove represents by 50% when fighting a monster that drops multiple types of herbs. These gloves can be obtained as a reward from Fist of Guthix and will crumble to dust after 100 such drops.

Picture Name Requirements
Zybez RuneScape Help's Image Irit gloves 50 Herblore
Zybez RuneScape Help's Image Avantoe gloves 60 Herblore
Zybez RuneScape Help's Image Kwuarm gloves 70 Herblore
Zybez RuneScape Help's Image Cadantine gloves 80 Herblore