Put full melee gear, such as iron full helm, iron plate, iron kite, iron legs. Vambs too. Anything that reduces your magic attack. Get an earth staff, buy water and body runes. You can get water and body for as low as 4 and 3 each respectively. Use Curse, if I remember correctly it was the level 19 spell. You gain 29 exp per cast, and it costs as low as 10gp. You'll most likely have to pay more than 4 per rune though. There's a zammy mage in varrock castle, cast your spells there. I believe it was around 25k exp an hour.