I was / am pretty into powerlifting. I entered a couple amateur events at 181 (didn't do too well) and 220 (closer to my natural weight, and so much better)
There are a couple keys to bulking up naturally. In general, you will never add serious muscle without adding at least some fat, but to minimize fat gains, you should keep your macronutrient ratios around 40% protein, 40% fat and 20% carbohydrates. Moreover, you want to consume at LEAST two grams of protein per pound you weigh currently. So, if you are a 200 pound man, you are looking at 400 grams of protein minimum. That's a lot of protein, and far and away more than the average person eats. To give a (poor) example, you'd have to eat 16 big macs to achieve that.
Usually a protein shake is going to have around 40 grams per serving, so taking two servings before and after you work out, and one or two before bed is going to go a long way towards reducing the volume you need to eat. So while they're not necessary, unless you can eat like a heifer, you'll need them.
The other keys are working out hard, and getting a lot of sleep. Stuff like creatine and fish oil help too.