Gaining weight is just a matter of eating more CALORIE. When you managed to find your calorie maintenance value, eating more than that will make you increase your weight.

Do you need protein powder? Not compulsory. If you have already outlined a good, balance diet and you've noticed that you can't meet the required amount of protein needed, then go ahead with the whey/protein powder.

I'm a amature on this but i gonna give my point of view.

So easy to gain weight but what i meant is not gaining lean muscle but gaining fat too on the way through dirty bulk.
I havent use supplement yet, but why don't you eat more using real food bulking then + protein powder for the protein intake?
Getting carbs is easy but getting protein is hard. Plus eating food is more enjoyable then drinking "substances" no?

Same spot i have tummy too, time to watch what you eat rather than dirty bulk and add cardio? i am so lazy to do cardio during dirty bulk and that was a big mistake.

What's your goal actually?
Add proper diet + rest, whey protein is not necessary.

Build your entire body.. Not just your chest, abs and hand..
Back, legs and shoulders too..

Yup,supplement do helps with weight gaining.try stacking Mass Gainer with Creatine,amino acid.dont forget ur solid food intake...no fast food to ensure clean bulking.Beside that do a lot of multijoint exercise aka compound exercise. (heavy ones).pm me if u need to ask anything bro