I've done some basic item flipping with items such as pure essence, raw monkfish and cheap Barrows armor but my cash pile is at 62M now, so I want to start flipping items that yield a better profit. I just can't figure out what kind of items because everything is so unstable! It's all either rising or dropping like crazy...

I find that items like those yield higher profit percentages than flipping the more expensive items like claws, DFS, bandos, godswords, etc.

I see. I have another question. With cheaper items I usually buy at 1.5% below medium price and sell for 1.5% over the medium price. That's 3% profit per item, which I've heard is the norm. Am I doing it right?

I am disappointed when my flips make less than 4%.

If you dont like the risk of predicting the higher price items that will change day to day, then your stuck with investing in stable items like raw materials as you'd said. The best thing about having 62million is you can invest all that into these raw materials. Buy different things, be buying and selling in all six of your GE slots!