Check the MP to give you a clue on some of the prices they sell for, well, the more common items.
If unsure of an item you found, just post in the Trade section using ISO ... you should get some answers there.
Also... check if there is a skiller ISO thread, check what they are buying and you can use that for junk items you would normally shrine or dismiss.
Good luck and have fun, but I think Bigheaded has a more in depth approach to the answers you seek.