Personally, I'd suggest the Karamja dungeonwhich is located near the Tz Haar zone. There are a myriad of options to choose from It is possible to mash them right there with a normal weapon OSRS Gold, food, and a bunyip if you can. Then, you could halberd them from a safe area or make use of range from a safe place, making it food free.
The other option is the cannon that you can test either on it's own, or in combination with all among the options above. Of the course, there's other areasto try, but I'd recommend this one in particular. I just realized that the title states greaters, while the blog says less.
If the task is actually larger than me, then my primary choice is the dungeon located in Brimhaven. You can choose any of the aforementioned options but you'll have to be wary of the terror dogs too. Unfortunately, there's no variety of options that are great for bigger dogs (no implied) however, you must keep fighting regardless of the situation.
Visit the Lunar Isle, use pure essence at the altar until you're proficient, then sell the runes on the Great Exchange, repeat. When you've reached 82 Runecrafting the ability make two runes with one essence Buy OSRS Accounts, thus increasing the amount of money you earn by twofold. Astral Rune is needed in Dream Mentor quest.