Take muddy keys towards the Lava Maze and only take the valuable stuff (you should not take the anchovy pizzas). This is the most RS gold efficient method to earn cash from f2p. I could earn 400k/hour if I'm good. However, muddy keys are expensive and require a long time to purchase. Use a gem bag to get maximum efficiency. Mine adamant ore. This is how I work. It's not even necessary to have food if you are in the full batwing and shield. Hop worlds. It's not even necessary to consider it because the PKers are scarce in this region. If you want to prolong your travels and have more time, you can use superheating to heat coal mines. But, I'm not certain if this is more efficient. 70 mining is necessary and 70 smithing for superheating.
Take on larger demons in the Forinthry Dungeon, use rune Arrows. This is the most powerful range of xp available for freeplayers and provides 100k gp/hour. I'm assuming that air runes are priced about 200k/hour on 66 runecraft. Of course, the higher the level of runecraft, the better. In the ideal scenario, you could buy a bond and cheap OSRS gold make money using one of the methods for members in the event that you only play for every day for an hour and already have decent statistics.