If you are already conditioned (been working out for a while) working in the 15 rep range whether 1 or more sets isn’t likely to illicit to much in the way of hypertrophy. It’s designed more as a sort of active recovery to give your tendons a chance to keep up with your muscle growth. Some people cut the 15s to one week or drop them completely but do so at your own risk. I’ve been doing that and now have tendonitis which is hampering my Chin Ups and Curls but then I’m also 50 years old and my tendons aren’t what they use to be. Also, many people dismiss the 15s as being too easy until they actually do an SD and then find that the 15s actually kick their butts.
Assuming you’re doing a full body workout 3 x week then I would stick with no more than 8-10 exercises. Also, I would make most of those by doing compound exercises since you get more muscles worked in total. I consider the following to be the best mass building exercises in the order listed:
Deadlift
Squat
Chin Up
Shoulder Press
Dip
Row
Shrug
Bench Press
To balance out the leg and push/pull exercises I would include a hamstring exercise and probably BB Curls for a total of 10 exercises. Note that Deadlifting 3 x week may not be feasible depending on the weight you’re using (considering your user name I assume you do them already

).
The reason for no separate Triceps exercise is that if you do the Press, Dip and Bench your already hitting your Triceps 3 times in a major way. OTOH Chins do hit your Biceps pretty well but Rows don’t as much hence adding in BB Curls. Your back will get hit 4 times Deadlift, Chin, Row and Shrug. Your chest will get hit 2 times Dips and Bench 3 if you make your press a seated incline. Your shoulders will get hit 3 times Press, Dips, Bench (more so if you do a slight incline bench).
If you really want to you can throw in a calf exercise but your calves are going to get hit with Deadlifts and Squats and if you’re like most people you can hammer them all the time and they will only grow a small amount (genetics). One way to incorporate them and keep the exercise count down would be to Deadlift once a week and substitute Calf Raises for Deadlifts the other two days, it just depends on how much you can get away with Deadlifting.
In the end if you want to get big fast then stick to directly working the muscles that make you big or look bigger (shoulders, traps, upper back, upper legs, upper arms) and let the smaller, at least appearance wise muscles like abs, forearms and calves get worked indirectly. You can always bring them along later once you've bulked up the rest of your body.