You should start to see gains in the end of the 3rd to 4th week. To obtain new muscle gains, it takes time to increase your cells and androgen receptors, and noticable hypertrophy to happen, you may notice water retention before this point, but that has nothing to do with the actual muscles, and more to do with the steroids effects on your kidneys by way of retention of electrolytes. Muscle gains don't happen overnight.