I really appreciate the comments posted by Chris, Dol, Scott and eindecker, they mean a lot to me.
To try and answer your question eindecker I will keep it short. You have already mentioned the stock necessary for stratch building, styrene strips and sheets of various thickness, I have a large stock of micro brass tube also aluminium and nickle silver tube, thin brass sheet is very handy but a lot can be made from coke can material, easy to work and strong. A collection of small nuts and bolts, there are many types available but all do a very good job. A good selection of wire, my wire ranges from 0.07mm to over 1.0mm, the wire has a multitude of uses. Most of these items have been built up over years of modeling but recently I purchased a soldering station, this is essential when building using brass tube or sheet, they are not a very expensive tool to buy, I think I paid around $80 for mine. My largest single purchase was a watch makers lathe, a very handy tool with many uses but not essential for the scratch builder. Normal tools like files, sanding sticks, various cutters, digital calipers, magnifiers, really good quality knives (I use scalpels) and tweezers. There are probably many more tools that would make scratch building easier but I make do with what I use to make my kit models.
Des.