I did no interview prep for JB and got hired on the first interview. I later did emerald coast when I was trying to go to a different airline and feel like the $400 I spent was wasted. Some guys swear by it. Ymmv. But JetBlue doesn’t expect you to do interview prep. They want to get to know you and make sure you did homework on the company and at least prepped yourself, though. Plenty of free gouge out there on the internet.