Don't EVER buy any gaining muscle mass workouts unless it has some of these traits:
1) A clear-cut nutrition system.
If you aren't eating right, you aren't going to see results- period.
The best gaining muscle mass workouts all have some kind of nutrition plan attached to make sure you're getting what you paid for- RESULTS!
This doesn't mean recommending a bunch of muscle building supplements either- those are a joke.
2) Easy to follow demonstrations and instructions on each exercise.
It's easy for some programs to just put a bunch of junk together like one or two pictures for each exercise and put it out there.
Don't take that stuff.
Some of the best work out programs have videos or 3D images that you can follow to make sure you are doing the exercise correctly. This is what you want- no mistakes!
3) Some variety.
You can't do the same routine over and over again for the rest of your life, you have to change it up on a regular basis.
Make sure your gaining muscle mass workout has multiple routines AND shows you how to change up your routine when it comes time.
Your body gets used to doing one thing over and over again, that's why you have to have variety to see big gains consistently.
4) Lots of satisfied users.
Don't use something that nobody's ever heard of- chances are it won't give you anything close to the results of a proven system.
The best gaining muscle mass workouts have hundreds if not thousands of satisfied users, so it's definitely something you should keep an eye out for.