Casein is better known for slow release and is generally taken at night so your body can work on building and maintaining your lean muscle while you sleep.
You can read all the fitness programs in the world, but none of them will do a thing for you if you don't use them.
A multivitamin may help, but it probably won't contain enough immunity-fortifying magnesium or bone-building vitamin D.
The best results will happen when you push your muscles until they can no longer do the lift or exercise on the last step.
My go to exercise for this is Dumbbell lateral raises as seen in the picture.
However, building muscle will be a lot harder to do outside of the 5-12 rep range.
Brown rice, quinoa and sprouted grains are complete proteins in addition to adding fiber and taste.