EDIT: Thanks for the input guys I think I'll just do some wcing (lvl81) till I get enough for green drags then probably move onto aviansies afterwards. Thread can be closed now.
Go kill those chaos druids under edge dungeon. You can make loads of cash there with no starting money as these things are only like level 13. Also be sure to watch out for revs cause I think they go wondering down there. Collecting snape grass is another decent method (below falador on the hobgoblin island).
With nothing I would go to seers village and pick flax. Getting 200k-300k should not take too long. Once you have that much buy some decent gear and go kill green dragons. Or if you want kill druids in either edgeville dungeon, ardougne, or yanille (depending on your theiving level). They will each weild about 300k-500k an hour depending on your stats.
Once you reach somewhere around 5m or so you can start merchanting on a low scale. Your returns will not be anything amazing with such a low amount but it is a good start.
Pick flax get some starter money. Buy rune pic, rune ax, or fishing gear. Mine/Woodcut/Fish until you have enough money to buy some decent gear to fight green drags. Go to green drags and get hides and bones. Once you have enough money buy better gear and keep doing green drags. Merch a little bit when you have some money too.
Thanks for the input guys I think I'll just do some wcing (lvl81) till I get enough for green drags then probably move onto aviansies afterwards. Thread can be closed now.