I'm not clear if you have any tube amp building experience, if not, my suggestion would be to study the classic Fender designs, specifically the Champ series because they are so extremely simple and effective. Most of the schematics can be found here:
Hi Scott, with regard to the schematics it is highly dependent on what tubes you have available and the goals you have for the amp i.e. clean, crunchy, high gain. amount of power in watts etc... My amps tend to be in between crunchy and high gain. The amp in the video is roughly 2 watts and built with semi-obscure tubes. The Fender Champ is a marvelously simple 5 to 10 watt circuit built with easily available tubes and not too much gain. The recycled wall-wart trick is nice because the transformers are cheap, unlike a lot of tube amp transformers because copper and steel are becoming quite expensive.
Using strings EAD, tune DAD. This of course is the same 151 tuning like GDG, but in the key of D using lower strings. On my CD 1 which primarily covers lessons for 6 string Open D Tuning DADF#AD, I also included DAD tuned CBG lessons.
Like stated above, the 3 highest strings GBE tuned GBD Open G tuning.
Maybe you can learn how to weave them into bracelets too? LOL
I assume this is always a problem. www.juststrings.com will sell you 10 string of any gauge you want. They will also make custom sets for you. This may be a solution. Enjoy.