In 1525, Albrecht Dürer published Of the Just Shaping of Letters (available for free from Project Gutenberg). Most of the book is instructions on how to make Roman Capitals. The last several pages contain "Directions for the Construction of the Text or Quadrate Letters". If you are looking for an authentic, later-period source for a full gothic alphabet, I present Dürer's own (translated) words and examples.
Note that there is no W in the majuscule letters. The I can be used for J, and the V can be used for U. The j is also missing from the minuscule letters, though it's easy to make one based on the i.