Currently, this is the most effective method.
Go over to the grand exchange and purchase "Molten Glass".
In order to buy it automatically you're going to want to price the "+5% button"
Level 1-33 | Beer Glass
Level 33-42 | Vials
Level 42-45 | Fishbowls
Level 49-87 | Lantern Lens
Level 87-99 | Light Orbs
NOTE: You can also train at Prifddinas, which is semi-afk and gives good xp.