Gear is only a part of it and even the guys on many, many grams a week will tell you that you have to dial in your diet. Start logging your food (and any non-water) drinks. There are some general guidelines, but everybody is a bit different, so you'll have to experiment with your intake. Sadly, diet is not as simple as "double the dose" to get better gains.
I would think that you would want to be as efficient with all of your resources (gear, money, training-time) on your quest to 18". Get the diet dialed in.