I would probably suggest starting with the green dragons above Varrock

Green Dragons from the Wilderness generally have a number of people inside them, but about 10 Green Dragons. Green Dragons in the Chaos Tunnels have few people, but only 3 Dragons. In the Chaos Tunnels, there's always a risk of the portal being naughty and hauling you to OSRS gold a random room. [Open the Spoiler for a map that shows the duration of Green Dragons from the Wilderness to a bank, in comparison with the Grand Exchange or Edgeville through the Chaos Tunnels]

I would probably suggest starting with the green dragons above Varrock, then, if your a bit unhappy with the sum of people/banking days, then switching into the Chaos Tunnel greens. For your green drags in level 20 over varrock, your very best choice is to find a couple of games necklaces, then teleport to clan wars, and walk a short distance east until you locate the dragons. Then, after your full, just teleport to bounty hunter employing the matches necklace, lender, and then teleprot to clan wars and repeat. It saves tons of walking, and matches necklaces are cheap and easy to purchase, or make whether you have a couple spare sapphires.

The chaos tunnel green dragons are a lot quicker and simpler once you get accustomed to them. Although they will use more food than the wilderness dragons, the convenience of being: 1) out of the wilderness (no revenants and their pesky teleblocks) 2) far less crowded (just takes 1-2 hops to Locate a world without anybody on this ) 3) Agree to some bank compared to wilderness dragons

All make it a far better place all around. In case you've got a home with a mounted glory and change, bring home teletabs/runes and recharge pray there then teleport to edge to bank/restart excursion. If not, use varrock teletabs/runes, bank in varrock east bank, and recharge prayer at the alter to the north. Enter through the dungeon entrance just over the"Mapped from Flippi273" box, and run south through the cavern then use the portal to get to the green dragon area. Ensure that you use up all your prayer before you start using food so as to minimise the amount of food you waste. Additionally, there are a few different spots you may use, such as the multiple spawns somewhat south of the lava maze in 40 wildy, which is always abandoned, however full of Old School RuneScape Gold revenants and only reachable by the portal sites. However, the Varrock ones are most likely best for drags from the wilderness.