Put muddy keys in the RS gold Lava Maze. Take only the valuable stuff. This is the most efficient method of making f2p cash. I can make 400k/hour if I'm good. But muddy keys are expensive and take time to buy. Use gem bags to achieve maximum efficiency. Mine adamant ore. I love to do this on the hobgoblin mining site. Wear full batwings, shields and food isn't required. Hop worlds. It's not even necessary to consider it because the PKers are scarce in this region. You can also superheat the coal by mining it to make your journeys last longer. I'm not sure if this is better however. Superheating is 70 miners. 70smithing
Kill greater demons in the Forinthry Dungeon, use rune Arrows. 100k gp/hr is the most efficient range of xp for freeplayers I know. I think doing air runes could be around 200k/hr on 66 runecraft, obviously the more you earn, the better. haven't done that recently though. In the ideal scenario, you could purchase a bond and earn money by using one of OSRS buy gold the methods for members, assuming you play every day for an hour and have good stats.