Welcome to the Civilization community, people who have as well been spellbound by the power that is Sid Meierism and, now, Jon Shaferism. I would frankly firstly suggest gradually, maybe after each game won on a difficulty, to increase the difficulty, because the most pleasure one can get from Civilization lies, when the A.I. and game mechanics are running at its best. In terms of playing the game as an empire building game rather than a war game, the only way to avoid the path of war is, coincidentally for Civilization V, to declare war. What I mean is that, at least for me, you have to find out all of the civilizations closest to you. After that, you need to ally with those civilizations and sign pacts of secrecy when they ask you to do so, lest you want to damage relations with your closest neighbors. Then, they'll eventually ask you to declare wars against the civilizations you signed a pact of secrecy against, but, because those civilizations are the ones faraway, you most likely won't have to combat any of their units at all.
Therefore, the act of declaring war but knowing that no violence would occur is the optimal way for which someone can be a Pacifist in Civilization V. Technically, you could just not ally with anyone, but then, on the later difficulties especially, you'll certainly be fighting wars of defense then with neutrality. In general, predecessors of the series had indeed generally laid off on the focus on wars for the easier difficulty levels, but Civilization V definitely took a more direct approach towards realism than the previous installments of the series, and, as history shows, wars and violent conflicts are the reality of history, and the Civilization series is a game essentially about the mechanics of history. What Civilization V has done, however, is most likely to give everybody more of a challenge, for all difficulty levels, to balance both empire infrastructure as well as empire stability from stagnation and outside forces, and I believe that such has only enriched the series to have more affinity with history and good gameplay.