Bugliosi's arguments get more and more ridiculous as he goes along. This is another version of his "I don't believe conspirators would do X, therefore there was no conspiracy".
First of all, just because Oswald was a cheapskate, it doesn't follow that he was poor. Second of all, if a person really was an undercover agent, he wouldn't be undercover long if he was in the habit of going on spending sprees. Third of all, we have a witness saying that Oswald came in to look at cars saying that within a few weeks he had some money coming in and would be back.
Yeah, I know. He was another liar. They were all liars.