Well there's the expensive way and the cheap way. Alching is the cheapest and good experience too, but the clicking can get a tad bit boring. I advice you bot it if you do alch.
You can superheat ores. Not the best experience, but no loss and a very low amount of profit. My bro did steel bars.
Using Ancient Magicks in Soul Wars' obelisk is great experience.
You can buy runes and cast the highest level spell you can (not recommended unless you got shit loads of cash).
You can also stunalch. It's basically a mixture of stunning and alching. You'll need a higher level to Stun though.

