Do you have any suggestions for merching armours and weapons?

I am unable to flip barrows, or any OSRS GP other weapon or armour for it for that matter. Tips? I will buy pretty much every item someone is trying to sell in a hurry to make money on it. Like my fury example. I also made 150k off the sale of a whip at 1 mil. Similar to that.

My flipping times are based on the price's trend. If its going up you can buy the item at the min price (how I determine the max and minimum prices will be discussed below) after which sell it for their maximum at the time the transaction is completed. Sometimes, i sell/buy for 1gp more than min/max, based how much profit I can make and how quickly i am able to buy or sell.

If the price of the item is declining, I will buy at min price and immediately sell it at the maximum price and still buy at min price. The reason I do this is because if I wait the sometimes 10 mins to buy the maximum price for an item that is falling then the max will fall over time.

Now how do I figure out the "true" maximum and minimum. I purchase 10 of an item more than the price and then sell the item for way under the price. It will refund me the money back when i buy for significantly more. Then it will inform me what it purchased for. When I sell for way less than that, it will offer me a lot more than I requested, as that's the price at which the min price is.

It will show me the most OSRS gold for sale recent max and min (more accurate that the graph) and will tell me when an item is about to go down before it is reflected in a graph. So what do you do? Would you be able to criticize or criticize me? Do you have any suggestions for merching armours and weapons?