While protein will definitely be an absolute requirement to build lean muscle mass, the second thing that needs to be in place is a good carbohydrate source. Carbohydrates will provide the energy that’s required to generate the lean muscle mass, taking your results up a level.
Typical muscle building carbohydrates that are commonly used include potatoes, raw oatmeal, fruit, pasta, rice, and bagels, all which are relatively cost friendly and easy to prepare.
These are all great sources to have with your muscle building diet, but at the same time, it’s nice to have a bit more variation in your day.
Some some forgotten sources of carbohydrates that you might want to consider are quinoa , beans and barley. I personally loooove barley, check out on my recipe sections for ways to use it 😉