The best protein supplements on the market now are pure whey or whey/casein--so if milk is allowed in your diet, you're set. If not, eggs *are* the standard by which other proteins are measured. Boiled is best.
Supplements called "Weight Gain" powders are generally "Fat Gain".
Weight training does not have to mean losing flexibility. Stretch immediately after lifting, and make sure you exercise through a full range of motion.
And for God's sake, don't use those wussy little "machines". They have no carryover value to any concievable human movement, let alone martial arts (and they're not very good at building mass anyway...).
SPC Jason C. Diederich, MOARNG
FEMAS, Bujinkan Budo Taijutsu, Kali-Silat
www.geocities.com/shaolinninjamarine