At 21, steroids will do more harm than good. Your natural hormonal cycles are still developing to maturity and taking anything now will interrupt that process and shut down your natural hormones, possibly for ever. If this happens, impotence, loss of sex drive, depression and many more problems would occur.
There are numerous educational threads on the main page. Take the time to educate yourself further. You get one body. Don't screw it up permanently at 21.
Most gains and losses in weight are a function of nutrition, for everyone, professional body builders included. I suggest you seek information on your nutrition and work with our experts in the nutrition section of this forum developing a nutrition plan to develop the lean gains you seek. If you don't get your nutrition right, you won't see the results you want and no drug (steroid or otherwise) will change that.
Good luck!
