Have reiterate some of the previous statements made in this post.
If your goal is to simply pack on size I suggest first picking a diet and training program to support this that fits your lifestyle and body. This should be more specific to your own body, but generally speaking upping the healthy fats, proteins, carbs, and overall calories is a good start paired with high intensity internal training. I personally like drop sets pair with a high calorie diet.
In terms of supplements this should be the last priority on the list. Keep it basic to start multivitamin, fish oils, vitamin d, Zinc/Magnesium, Creatine, Aminos, probiotics,and basic hormone support (ashwagandha/anti-estrogen). Unless you are running gear I think the priority should be the diet versus the supplements. Supplements and even PHs will only provide minor support in gaining clean mass.