I camped waterfiends for OSRS gold those levels too. It is likely that you can kill them pretty fast. It is important to Bork daily can also help increase the blue charms. The burst of rock lobsters used to be great charms, however, I see it as somewhat unnecessary due to the huge amount of loss that you suffer. Cannoning the more powerful demons of the Forinthry dungeon also used to be a fast source of charms. But I'm not sure of the effectiveness the cannon is in eoc.
If you are camping with on the waters of the world, you'll be equipped to acquire the charms required for 774 before the quest comes out. It is important to make use of your spirit rubies, gemstones, etc. while you train! Also think about doing a quest such as While Guthix Sleeps or Blood Runs Deep both of which can give you a huge amount of knowledge that you can make use of when summoning.
I'd recommend Slayer. Slayer lets you encounter an array of creatures which all give you plenty of money usually. It is up to you from that point on , which is your favourite monster to kill.
Blue Dragons are excellent money The downside is that it requires 70 agility it to become efficient. As of now, you may kill Black Demons, for money, perhaps. The best gear for you (considering your financial problems) could be:
Melee-Guthan's Equipment (Around 3M, but it doesn't require food in a slayer that can be meleed task) Garments of the Verac (1.5M includes an opportunity to pray) A ranged set is recommended. Karil's set. I'm unsure of the price though. There is always Royal D'hide, which is at a nominal cost. MageAhrim's set is 1M. It is possible to upgrade to buy 2007 runescape gold Ganodermic for around 3M.