Here's a super easy way to read the graph, sorry small children, I don't mean to insult you!
Click on each of the options (did you know you could click on them?) until only the green and orange lines remain. The ones you grayed out show volume of sales which only tells you how popular the items are. While this is valuable information, for most items it isn't necessary because you already know they are popular from using them yourself frequently. Now, the green line is sell price and the orange line is buy price. These are averages of averages, so you will see values above and below these values. Anytime you notice a gap between the green and orange line, then that was an opportunity to sell.
A consistent but profitable market will have the green line frequently spiking upwards while the orange line remains relatively steady around a certain price. If you see such gaps, then you have found something worth flipping. Provided that the gaps are somewhat frequent.
Problem is, most items don't rise and fall enough to make a profit
just from flipping. So you need to improvise in other ways... like
I place buy orders on salvage materials (there are multiple items that you can purchase to salvage into the same materials)
at the bottom value. Then I purchase crude salvage kits with karma to
turn those salvage materials into their respective tier's loot. When I sell, I usually take a very small loss or a huge gain, which averages out to a profit.
Go explore some new markets and see if you can't predict your profits before you even start investing. Don't interpret failure as a deterrence, but instead as a way to learn new lessons.