As has been noted, making ‘real’ shoes, with insoles, isn’t exactly
easy, but it’s not rocket science either.
Once upon a time, I used to do a lot with the Society for Creative
Anachronism. (Pretend to be shocked.) A then-friend of mine was
pretty seriously into shoe making. He did a couple of workshops on
how to make custom fit, lasted, insole shoes. It’s not simple, but
it can be done by hand, with pretty close to the normal tool mix a
jeweler would have on hand. (Figure $50 in leather tools, and about
$100 in leather. Which gives you enough leather to do several pair.)
You start off making plaster casts of your feet, beef those up with
bondo and wood, and then use those as lasts. If you dig around on
SCA.org, you may find some links to ‘how to’ articles. I’ve contacted
the last email I had for the person I knew who did them, I’ll let you
all know what comes of it, if anything.