The average man produces 50mg to 75mg a week of testosterone on his own. By taking 100mg a week all you are gonna do is stop your natural production to have 25mg more in your system which will do absolutely nothing to benefit you. About gaining weight, it's not like you are gonna take 500mg a week and add 10 pounds of muscle without lifting weights. What steroids do is enchace whatever you are training on. If you train for stamina it will enchace your stamina, if you train for explosivness (mma-kickboxing-wrestling) it will enchace that, if you lift weights you will gain weight/muscle mass. My advice, take 300mg or more cause less than that won't do anything beneficial,it will just stop your natural production for nothing.