I've been looking to start my first build up of a bike, but I wanted to know which type of steel I should be looking at getting. I know a bike is a bike, and I'm not terribly conserned with weight, but are there any that I should just say no to? I currently have a Guerciotti made with Columbus SLX, but am unfamiliar with Reynolds or any of the Japanese tubing, or other "materials' out there.
Your questions must be answered with more questions, as you fail to provide any context for the bike in question. You have an italian bike designed for racing - what is the intended use for your new build? How much are you willing to spend? And be warned that opinions on this matter will vary - some will argue that it's not the steel, it's the care spent in constructing the frame that counts.
In my opinion, a vintage bike that is intended for frequent riding is one that is manufactured with care, and built up with good-quality components that suit the bike's intended purpose. Type of steel is an important variable, but it is just that: one, of many, variables.
Back to your original question: here is a link to a chart that lists a variety of manufacturers' steel tubesets, their weights, maximum rider weights, wall thicknesses, and intended usages:
Reynolds, Ishiwata, Tange, Columbus, and True Temper all have good reputations for manufacturing high-quality steel tubesets (there are others, they just don't stick out in my mind right now), but again - a badly built-up bike made from the finest steel will still be a pain in the arse to ride, and end up sitting in the garage.