Bench press. More exersizes do not mean you will gain more, but will probably inhibit your gains somewhat. 2 exersizes would be okay, but one would be even better. Concentrate on moving the plates on either flat or incline bench press. Pick one of those, lift on it for a month or so, then switch to inclines for a while. You will be amazed at the progress you can make if you switch rep schemes about every month and eat enough. Comound movements are the best mass builders, period. Even bodybuilders know that. These guys (gym rats, bodybuilders, and even novice lifters who know jack**** about lifting) like to make you believe that by performing tons and tons of sets on about 6 different exersizes will ensure quicker growth. However, this could be no further from the truth. Simply do something like,
Twice weekly
Bench press 6x8-12
You could also use incline press.
Concentrate on performing one extra rep per set each workout, or at least gaining a couple of reps throughout your sets. This will tell you that you are progressing, and in turn, getting bigger! If you take in enough calories and perform the compound movements there is a very good chance that you will get the results you desire.
P.S: Don't over do it on the assistor muscles either. For a while, I would leave out the direct tricept isolation and cut down on the shoulder work since you are performing 6 sets of bench press twice weekly, which means your tris and shoulders are already getting a good amount of work.