The thing about weight training is that everyone is differnent. What works for one person, might not work for another.
So, just because your friend gain consistently doesn't mean you will. To find what works and what doesn't, you should use a diary and write doiwn the exercises, and see what is making you gain mire muscle and what isn't.
I like to change 1 exercise per muscle group each week so that i know which exercises work with other exercises and which don't. You should do this for yourself as well, as everyone is different.