The foam muscle suit is the cheapest/fastest way to obtain the results you want...that being said, if you want a muscle suit that will mimic the natural movements of the body/muscles you'll have a lot of engineering to do. You have to design the muscle using the "Tendon/muscle" movement.
By that I mean that each muscle will be attached by a tendon to respect the body mechanic. Built a series of "bracelets" (for your arm, you'll need 3: arm, elbow, wrist) to those you'll attach a "muscle" made out of a rubber compound: i.e. stretching latex material. The muscle will be shaped in flexing position. For example: the bicep is bulging; by attaching the biceps to 2 "tendons and 2 "bracelets" and positioning the 1"bracelet" just under you shoulder, at the top of you real biceps, and another "bracelet" pass you elbow, you'll be able to stretch the latex muscle in a normal position.
As soon as you bend your arm, your bicep will bulge as in real life. Studying the body mechanics is also a good point of reference.