If you seriously want to try it from schematics, I would recommend getting a few books like these:
And at the same time start trying to find the schematics for an amp that you would like to build. There are several sites like this:
If cost is an issue, You would need to take into account the prices of the tubes, etc. This is the way I am going to go.
I haven't soldered very much except pups and harnesses myself over the years; but while I was in elementary through high school I used to wire components for custom recording consoles for a company in L. A. My mother and my older brother both worked for the place and they would (under) pay me to do some of their wiring (which they would bring home). Of course they taught me very well and were constantly overseeing (and testing) all of my work; but I got pretty good and learned a lot. The main practical thing I learned was that schematics are maps with a very clear and understandable "legend" once one learns the symbols. Then, if I got stuck, I would just ask somebody. So my main concern simply became making sure that all of the connections were made and made good.
Writing schematics, now that's a hole 'nuther bucket of fish bait!
What you will be doing is building circuits from schematics, so these above books, or other similar ones can give you all that you need to do that. I would suggest reading the book on schematics entirely and keeping the others mainly for reference; but I'm sure there would be chapters for any area that you may feel weak in too. I don't think you would have to read all of the "Electronics for Dummies".
I'll bet that if you have the bug now, you will love the whole experience of it once you get started, even if you make some mistakes along the way. There's nothin' you will run into, short of breaking a component, that can't be fixed.
Then, of course, you will also need to build some sort of housing for the amp too.
If that sounds like more than you want to tackle, like I mentioned above, there are some very cool kits out there:
I hope I have given you at least a little direction in this very cool endeavor...