My advice on this would be: You dont really play for domination until you have the blackpowder guys with the bonus against horses (I dont know what they are called in english). Until then, you play the same as if you were going for space-race. Focus on economy, trying to get a tech-lead. Then build-up and start making war. Then comes another pause, where you build you factories. The AI does this very late. You will end up with a tech-lead and a production capacity of two AI-Civs combined. And Infantry when noone else has them yet. Only then you start pushing for domination. Once you started conquering, you will notice that your economic build-up phase was not only needed for acquiring the tech-lead, but also for maintaining your gains.
I dont do domination often at all, so others may well have a more solid and different opinion on this. Last SP-game, i actually did make it for dominiation and it was a close call, not because anyone posed a threat to me, but because i had to invade another continent in order to get the needed percentages and maintainance-cost almost killed me. I had my science at 0% and still lost a couple of hundreds each turn. The turn the borders expanded, making me win, was exactly the turn my army started to desintegrate (1963, large hemispheres, prince, epic).