Welcome to my guide.
I made the guide so that people can have it open in the background while doing Herblore rather then having to click the skills tab and deal with opening/closing it. I decided to make a method to 99 because some people prefer being really efficient and some people just like to progress to Overloads and don't care for other potions.
(Level Required) (Potion) = (Cleaned Herb + Vial of Water) + (Secondary Item)
Hope it becomes of use.
Overload Method to 99 Herblore
(1) Attack Potion = Guam + Eye of newt
(12) Strength Potion = Tarromin + Limpwurt Root
(30) Defence Potion = Ranarr + White Berries
(38) Prayer Restore = Ranarr + Snape Grass
(45) Super Attack = Irit + Eye of newt
(55) Super Strength = Kwuarm + Limpwurt Root
(66) Super Defence = Cadantine + White berries
(72) Ranging Potion = Dwarf Weed + Zammy wines
(76) Magic Potion = Lantadyme + Potato cactus
(88) Extreme Attack = Super Attack + Avantoe
(89) Extreme Strength = Super Strength + Dwarf Weed
(90) Extreme Defence = Super Defence + Lantadyme
(91) Extreme Magic = Magic Potion + Grounded Mud Rune
(92) Extreme Ranging = Ranging Potion + 5 Grenwal Spikes
(96) Overload = Torstol + Extreme Attack, Extreme Strength, Extreme Defence, Extreme Ranging, Extreme Magic