After browsing the runescape forums for quite a while I have found out about some of Jagex's secret rules on how the grand exchange works I will post them here. Since I am not one of the people who found out about them I do not want credit for them in the guide I just want them added.

 

 

 

1) You cannot instantly sell an item you've just bought in the GE at a greater price for at least 4 hours

 

 

 

2) You can only buy 25k raw materials every 6 hours or 100k raw materials every 24 hours.

 

 

 

3) You cannot sell/buy more than 100 manufactured goods at once (bows, armor etc)

 

 

 

4) Your transaction will not complete if after your offer has been in the system for a while, the prices change resulting in your price falling outside the price range for the items you are selling/buying. (This IS noted in the knowledge base but not widely known and often forgotten by players, so I included as a reminder.)

 

 

 

Debunked Rules:

 

 

 

1) You can not sell or buy an item from someone currently logged into your world.

 

 

 

2) You can not sell or buy an item from someone you have recently interacted with.

All added, thanks.