Lardar pretty much summed up the best methods, but to OSRS gold make a correct plan we'd need to know exactly what level you are. Oh, and good luck! It depends how you want to do it, personally, I hate runecrafting and don't require the cash, so I slay constantly at the moment for effigies to use on runecrafting, in addition to helping people with their RC effigies, (91 onwards, so I'd suggest this as it's a totally free 30k rc XP a day) I'd use the penguins too for a fast boost once a week, as that accumulates well to a top XP count...
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