The best way to gauge how much you should risk per trade is simply risking what you feel comfortable with; ask yourself if you can handle 10 losses in a row on your current risk amount per trade, if you can handle that and not become emotional or blow out your account then your risk level is probably OK. These are gimmicks folks, they sound really good, but in reality they are just wasting your time and masking over the reality of what it takes to trade successfully, and that is why combining complicated and messy trading methods with price action is the a deadly trading sin.