Past like the first 30 minutes? How about buying the high every time there's a new high? This method would only lose money when price makes a new high and then drops under it. The method would only lose money on days that look like this /\ true?
Where do you place your stop and profit targets? How do you define the high? Is it the high after the cash open? for that 24 hour period beginning with the overnight session? The high between some arbitrary time intervals? What if there was a higher high in the premarket and spot is now down from there after the first 30 minutes? What if the overall trend is down but you get a spike at cash open? How do you define a higher high in premarket? How do you define a spike? How do you define an up day vs down day? How do you know the high 30 minutes in isn't the overall high for the day when you buy it? Not trying to be a d*ick but I already tested something very similar to this
Just backtest it. No need to speculate when it's pretty straightforward to find the answer to this hypothesis.
why everyday? why do you have to exit at the end of the day? day trading is for cowards who can't handle any risks. grow a pair... look at long term charts... why exit at all?
After you master that, you can furthur improve your system by simply also buying the low of the day. It would only lose on days that look like /\ true?