When training in the dungeon, It is very important you always have protect from Melee *ON* Without it you may die in seconds. The best gear, would be the highest range armour you can wear aswell as any other equipment that gives range bonuses, the higher the bonus the more exp. You need NOTHING giving defence, concentrate it all on range, and if it doesnt effect your range bonus, some pray bonus stuff too. I would recommend taking range potions so you fully take advantage of the chinchompas. A cannon is not used at the same time, All though, thinking about it, it might help get more monsters near you. I would recommend going round under the shelter bit of the second corner after the level 149 skeletons first start spawning.