Before you look into any supps
What does your diet look like now?
What do your calories look like? What are your macros?
how is your current weight gain?
What training are you doing? How many times a week? How much cardio are you doing?
All of these factors are crucial to outline what we can suggest on changing first on foremost before adding supps.
Then do you have your essentials covered?
Whey? Scivation, PES, Animal Whey, Blue Star Whey Smooth all good choices
Fishoil? 2-3g of EPA/DHA Daily (highly suggest OxiMega)
Multi? Animal Pak, Orange Triad, Vitamore
Creatine? Bulk mono take 5g for 30 days then 3-5g on workout days.
a majority of the time food is the problem with gaining size and strength. Adding pills and powders will not always result in good gains or quality mass over a prolonged period of time. Remember you cannot supplement a bad diet and training program.
Once everything above is addressed some great things to look into would be:
Ergonine (for overall performance/endurance)
ARA/XGELS
HMB-FA (clear Muscle)
LAX Products (Str3ngth Unleashed)