Just keep your life simple. Gaining weight is as easy as calories in vs calories out. Creatine is a waste of money and it won't do anything that milk, eggs, and red meat won't do. Protein is important, but in terms of supps, it is what it is, protein, nothing more and nothing less. If a powder helps you get what you need, it is okay, but look at it like this, what is a protein shake? 90 cals? Drink 3 a day and that is 270 cals, that won't put any weight on you. If I were you here is what I'd do.....
meal 1: 5 whole eggs scrambled, lots of bacon, 3 slices of toast with peanut butter and jelly, and a quart of whole milk
meal 2: foot long turkey sub, small bag of chips, and a quart of whole milk
meal 3: 2-3 servings of meat loaf, mashed potatoes, a salad, and a quart of whole milk.
meal 4: two cans of tuna with mayo, make 2 sandwiches with 4 slices of bread, and a quart of milk
If you wanna get crazy have a quarter of a Snickers bar after every meal
in between meals a shake or a bar is fine and bonus calories......but this is simple and do-able.....you don't need to be running around with tupperware containers filled with brown rice and chicken and you don't need to use nutritional supplements to gain weight and you don't have to run around carrying a cooler of food and supps like a fag, lol......do the math on the nutritional breakdown of a gallon of whole milk in a day, I doubt you'll even want to bother with supplements.
Eat a lot and keep it simple.....if you're in high school eat 2 school lunches, the real lunch not the french fries and nutty buddy line. Eat 3 helpings at dinner. To get big and strong you'll more than likely have to carry at least a little more bodyfat than you'd like, but you can probably stay fairly lean.....at 6' and 155 you're not thin, you're emaciated, so you've got plenty of room to grow....eat real, wholesome, calorie-dense foods. Between 8th and 12th grade I went from 160-ish to 235 without much change in bodyfat eating similar to the above outlined "diet" and we're about the same height.