A good multivitamin (AST Sports makes a good one), creatine (depends which kind you decide on), I find just basicworks well. Although you'll find advocates of every kind here on the boards. And lastly some form of EFA, like (You can find these anywhere now a days). Those three are some good basics to have if you aren't already using them.
As far as OTC supplements, it depends on what you're looking for. You seem to want to build some mass. Are you looking for more of a stimulant or a testosterone booster? Or just open to trying anything non-hormonal?