Killing Dragons is most likely the cheap OSRS gold most lucrative method for making money right now, because anybody with decent stats will be able to kill dragons. If your situation is similar to your stats , it's just a piece of cake.

Therefore, your choices are the Green dragons which are situated inside the Wilderness as I'm sure you've guessed It's simple to locate an empty world because quite many people don't kill Greens due to fear of being PKed. Blue dragons are extremely simple to take out, Taverley can be quite crowded and the Heroes guild but it's not that difficult to find the world that is empty. The W117 Heroes guild tends to be empty. If you've at least level 60 Dungeoneering you can access Taverley resource dungeon.

Red dragons not really recommended as Red dragons can be located in two locations if I'm not mistaken: Red dragon island in the Wilderness and Brimhaven dungeon and both are far from a bank Dragons of the Black - Taverley is crowded everywhere I would not bother, so Zanaris is your best bet in my opinion.

Metal dragons: Not too much to say about them All Metal dragons can be found in the Brimhaven dungeon (Mithril dragons being the sole exception) and aren't difficult to kill and come with decent drop rates; Frost dragons require 85 Dungeoneering is required, so it's not a viable option right now unless you're looking to learn Dungeoneering. You can also try to earn money from Slayer however, unless you're getting daily tasks from Dragons, I'm fairly certain you'll earn more money by killing Dragons.

What Silv said are all pretty good buy runescape 3 gold suggestions. At the time I was on your level I made Experiments. All the way from 60-70 and it took me three days. It was dull as you're not really gaining anything except for experience however.