My last two games have been on large and continents at Noble and Prince. In both I stressed founding religion(s) and spammed missionaries, but the key has been to attack and eliminate the 2 or 3 rival civs on the continent being careful not to expand too rapidly and incur excessive civ maintenance costs. I then focused on research leading to caravels and circumnavigated the globe for the extra and very helpful movement point while settling to expand my borders so the AI couln't come and found cities on my continent. This way I was able to concentrate on building and research and did not even a single musketeer or rifleman and only a couple of knights and grenadiers. Both ending in domination wins about 1900 A.D. I learned the hard way not to tolerate aggressive civ neighbors even if they are pleased with me and do not allow open borders unless I have a very specific useful purpose. I have kept barbarians somewhat more tolerable by stationing second-line units to reduce the fogged out areas to reduce their generation, at least in the most critical areas. In the first game I was Caesar and the praetorian units were helpful with early conquest but needed accompanying axemen to protect them from other axemen.