1) Is a workbook necessary if I supplement the text with the official teacher's manual, and online drills and exercises provided by universities teaching with Athenaze? I cannot find an example of a workbook without buying it, and I do not think an answer key exists--so am hesitant to purchase if I can find other resources that accomplish the same thing.
2) At the beginning of Athenaze, only nom. sing. are given for nouns, and gender is indicated presumably by article. Later in the book, it looks like it follows the form of Mastronarde and gives nom. and gen. sing. when introducing new vocabulary. I have gone through a handful of units of Mastronarde, and gen. sing. is always introduced with a new noun, as well as gender. I am not at a point in Mastronarde where it becomes clear why gen. forms need to be memorized with the nom., but I assume it is often irregular, or is used in a stem, or some such thing that will eventually become understood.
I like to learn fairly systematically. Is it advisable to go through and memorize nouns in both nom. and gen. sing., as well as gender, despite how it is introduced in Athenaze?