I would download files from openev sources on the Cap K, and if you want more traditional literature reading start by reading Marxism literature and then expanding based on what you understand and don't understand. For a beginner, reading through the full cards on cap files should be a good starting point though.
You confuse the terms "Double Turn" and "Straight Turn." A straight turn of a disad or advantage is when you only respond with turns and you provide no defensive arguments. A double bind is when a team (usually the neg) puts the other side in a position or points out they've put themselves in a position where they have to concede one of two things Easy Example: The Disad is a generic that applies to all substantial plans, alongside this disad you could run T on substantial that prevents the aff from being able to no link the DA by saying they aren't big enough to trigger, because that concession wins you the T argument. There are theory arguments for and against double binds. Rule of thumb just try to avoid putting yourself in a double bind.