Hello, welcome.
Just do one country or region at a time.
The value currently in the marketplace, on
ebay or Delcampe perhaps, or on Delcampe Prestige for expensive stamps (to purchase and search) is less than the catalogue price stated usually, but for quality and rarer examples, the price is no object sometimes!
Fun and the hunt are a part of stamp collecting or philately.
Specialized catalogues are almost a necessity for valuable stamps, and an expert's opinion helps too. Lots of those here.
When you post, please try to name the topic / thread with the name of the country, if you know it. This helps to attract those who know more about those stamps.
This Italian site (in Italian, but stamps are stamps!) is a nice site. I do not have much experience with it though.
http://www.ibolli.it/index.phpItalian stamp varieties :
http://www.italianstamps.co.uk/vari...s/index.html