Soft Clay method:
Clay= 92-97 gp
You can purchase clay on the grand exchange, or use one of the handy auto scripts to mine yourself some clay. Now here's the boring part which makes this method a little tedious, thats why if you are good with scripting i suggest you make a script for this and perhaps share it. You need buckets of water to combine the clay to make soft clay. Right clicking the clay will allow you to make "X" amount of soft clay saving you from having to click one at a time.
Now with your soft clay head up to the Grand exchange.
Soft Clay= 170-187gp
Thats almost doubling your money!!
Lets look at an example.
100k investment to buy your clay
Thats apx. 1000 clay
Once you combine your buckets of water and turn it into soft clay and sell it
for 187 gp each.
your new worth will be 187k!
Note: This method is the method I use when I need arrows for ranging, need a quick batch of food for training, etc... You can become rich off this, but you will be combining a lot of buckets of water. As long as have 100k you can make a quick 87k profit for arrows, food, and whatever it is you may need for your auto-er.
Another method that is similar to the above, but not quite as profitable is Mith bars. I've tried this method and the it doesn't give as much profit as the above, but if you're looking for smithing xp, as well as a little cash then this works great.
Buy the coal and Mith or mine it.
Coal= 180gp
Mith= 150-190
Mith bar=1184 gp
You will need 5 coal per mith bar so that adds up to
coal x 5=900 gp + the one mithe ore = 1050 gp.
thats about 100 gp profit per ore.
Like i said its not as beneficial as the clay method but it can give you good smithing xp, I used it with Irokies Al-kharid smelter, and it worked wonders!
I hope you found this tutorial helpful and hope it funds you're autoing needs as well as mine.