I didn't keep as detailed of a log this time around, so hopefully there isn't anything crazy inefficient going on at this point.
I spent until turn 188 filling out my part of the continent and building up a stack of elephants and catapults pointed at Portugal. Here's my empire at it's height, on the eve of war with Portugal.
Portugal doesn't put up a meaningful fight. It's simply a waiting game while the catapults do their job, and then my dozen or so elephants make short work of whatever city defenders are present. After securing the continent, Joao capitulates.
A couple of turns after finishing Portugal, Rome surprises me with a declaration of war. I wanted a war with them in the near future, but I was hoping to consolidate my gains and tech into gunpowder units first. At this moment, I have nothing but 3 or 4 archers in the area.
Rome takes my first 2 or 3 border cities, but my elephant / catapult stack arrives just in time to push back the invasion and reclaim my territory. Rome is fighting with knights, trebuchets, and mustketmen, so I have trouble trading favorably. I do what I can but the front stabilizes with Rome reclaiming their initial conquests. I lose my stack in counter attacks, but I'm rebuilding with janissaries and cuirassiers.
Turn 251 Saladin drops an amphibious invasion on my shores. Rome moves up their first riflemen, as well. I can match cuirassiers and I'm only 3 turns out from cannons, but I have nothing left to upgrade and it was taking all the production I could muster to keep the status quo with Rome before rifles.
I think my mistake was taking too long to hit with my late classical push. By the time I had finished my expansion and had a stack ready to go I was attacking into medieval armies. That's fine if you're bullying a weaker neighbor, but I was too far behind to deal with an equal.
Alternatively, I should have pushed for optics quickly, and tried to play tech broker between the continents. I never made tech parity on my own continent, and the other continent was even further ahead.