At 20 your natty test levels should be firing, check you diet out if you have hit a wall you may look to some of the basics dependingon supplement exerience sch as a basic creatine however more often than not its nutrition holding people back, ask yourself am i eating for growth? Do i get 6-8 small meals in every day? Do i hit 1.5g of potein per lb of bodyweight? Do i take in good healthy fats and ar my carbohydrate sources correct? If any of these are no then start there. Many people cant eat or dont have the appetitite so e released Ravenous to aid this, that mayhelp but other than thamany companies offer good basics, whey protein,amino's and creatine.
I hope this helps