The Market Interface of Eve-Online is nothing sort of the most confusing thing ever made, but it can be mastered with a little bit of work. The easiest way would be simply to play with it, and look up anything that you do not understand. There is some things that everyone should know.
You are always buying from the cheapest buy order at that station even if you select the more expensive one. This is a hard concept to grasp, but when a person make mistakes on buy orders or select to purchase a more expensive order they are ALWAYS buying the cheapest order at that same station. The person who has the item up for sale at the low price will receive the more expensive offer.
This goes contrary to how the real markets work. It would be like going into the store and picking up some apple jacks for 2.50. Then you go to the cashier and give her 3.00 dollars because that is what they cost in the store down the street. The other option would be going into the store and yell out that you want to buy apple jacks for 250 dollars because you forgot the decimal. Someone then hands you the apple jacks and you are forced to pay them 250 dollars.
This is why it is important to not make mistakes. Be sure of your decimal points and amount of zeros before you place the buy order.
