As a beginning pizza maker I wouldn't be overly concerned at this juncture about the technical aspects of pizza making. Rather, you should try to find good dough recipes and learn how to master them. If you are so inclined technically, you can later learn how best to use dough percentages (baker's percents) to change recipes (usually to scale them up or down or to change pizza sizes, etc.). That said, however, I believe that you should pay rather close attention to the ratio of water to flour (the baker's percent that represents the degree of absorption of the water by the flour). Often, the amounts of flour and water are specified by weights rather than volumes. If you plan to use weights (as opposed to volume measurements), I would recommend that you buy a good digital scale to weigh such ingredients. It will spare you a lot of sub-par or failed doughs during the learning process. You will also get a better feel for what a good dough looks and feels like.
Gluten flour, also known as vital wheat gluten, is a dried wheat protein of high-protein, hard wheat flour that has had all of the starch removed and is then dried. Although there are slight variations from brand to brand, vital wheat gluten has a gluten content of around 45% and a protein content of about 75%. As fellow member piroshok has indicated, it is often used to strengthen a weaker flour. It is also used to give greater height and volume to breads that incorporate a lot of heavy ingredients, like dried fruits, olives, and nuts, and to supplement flours that themselves have little or no gluten content, like rye, soy flour, etc. The recommended amount to use is typically at the rate of 1 to 2 teaspoon for each cup of flour used (or 2-3% by weight of flour, in terms of baker’s percent). Adding vital wheat gluten to a weaker flour to increase its protein and gluten content will not yield a product that is identical to a stronger flour. But I believe it improves the weaker flour and yields a better product than without it. I have used vital wheat gluten on many occasions, such as when I did not have access to bread flour or high-gluten flour but I had access to all-purpose flour. I simply added vital wheat gluten flour to the all-purpose flour. In fact, I recently reported (very favorably) on such an experience with a NY style dough based on all-purpose flour supplemented with vital wheat gluten (and also dried dairy whey). See, for example, Replies # 203 and 204 at the Lehmann thread, at http://www.pizzamaking.com/forum/index.php/topic,576.200.html
Given a choice, you should try to get high-gluten flour for those dough recipes that call for it. However, I know that Canadian members of this forum have had a difficult time in the past getting high-gluten flour in Canada at the retail level. I don't know if King Arthur or other sources of the Sir Lancelot (or other brands) of high-gluten flour ship into Canada, or at what cost, but, if not, you should look for Manitoba flour, as suggested by piroshok. I don't know the exact protein content of Manitoba flour, or even where or how you can find a source of it in Canada, but high-gluten flour usually runs from about 13.5-14.2 percent. That might be the benchmark you want to use.