Wait till your 25. Not trying to sound like a downer either, but the pros consume WAYY higher dosages of AAS then anyone here would recommend along eith staying on it year round. I'm talking 2-3 GRAMS of test alone not limited to their other 20iu hgh regime, insulin, and other anabolics and diuretics. And these guys have the genetics. The key to building muscle is TIME. Not drugs and pills. Especially at your current weight, you need a good base atleast. 60kg isn't a good base for your height(not bashing you, just being honest). Assuming your an average guy(no underlying medical consitions that may hinder your muscle building), you should be able to get around 200lbs naturally which is like 85kg I beleieve(not positive). We all wanna look like jay cutler or ronnie. But you have to think. Do you have the genetics? Do you have the money? Do you have the time? Are you willing to sacrifice doing jobs you might not wan to do? These are all things pros have accepted along with the high potential for health risks. I wish you the best of luck. One last thing, remember that your health should always be #1. What good will being 300lbs of solid muscle be if you happen to get kidney failure or a heart attack from abusing AAS.