The book you need a credit card for is TSPA, and at 6' and 150, I gotta suggest you do THT. You're actually on the low end of normal weight, and at 13, the hormones are going to take care of what I'd bet money is just leftover baby fat. The THT book is free, available from the main page of the site, and you should start there. You should also go back to musclehack.com and hit the link for the "best bodybuilding diet ever" on the right hand side of the main page. Also, here in the forums, you will find the Free Workout Logs section, which you can peruse and pick out one to use. Modifications should not be warranted and are typically best avoided, but if a specific move gives you issues we can certainly talk through that.
Ultimately, my best advice to you starting out, for one, I hope you get routine physicals, and if not, tell your parents you are starting a workout routine and ask them to take you for one. For two, it is
absolutely imperative that you know how to execute the moves in whatever workout plan you choose. I have to strongly recommend that you watch the videos here as well as
www.BodyBuilding.com (they're clearer and narrated, plus there's way more of them), and start with very light weight until you know you can maintain correct form throughout. You are very young and still growing, so an injury caused by poor form will be absolutely disastrous for you at this juncture. Please consult the staff at your gym on how to operate the equipment. They should be more than happy to show you how to operate every last machine they have. Just like with free weights, do not go heavy with the weights until you know you can use the machine correctly.
As to recommendations for you specifically... until you do your homework and take the plunge, we're not going to have enough information to go on. Familiarize yourself with your gym, get your form down, then pick a week of when you're going to do it, and then go at it. It'll generally take only a few weeks for you to identify your weaknesses or issues, and then you can go about tackling them once you know what they are.
