Diet and intensity (you do not necessarily know whether you will respond better to high volume or low volume yet.. perhaps you should experiment with different volumes and frequencies as long as you stick with something long enough to be sure that it is working.. this means eating properly, training properly, etc. - alternatively, you can also cycle volume) are probably of more importance. What are you eating right now?
Also, see the "Do this Routine instead of that dumb one" thread if your goals are hypertrophy based, perhaps WS4SB or 5/3/1 if your goals are more strength based.
Also, you probably want to gain way more weight than you are currently shooting for at your height.