[Beorn]

C3C is all about numbers and getting exponential growth out of your empire.

In MP, the map type and AI/barbs setting are very important because they influence how recklessly fast you can allow yourself to grow.

You want to push a couple of warriors then several settlers early: grab food sources with your first wave. Make potential workers and settler pumps, each of which will get a granary; we're talking about 3-4 cities here, including your capital - the others probably will lack either food or shields to pump a settler out every 4/6, or even a worker every 2. This is the REX opening. It generally beats any kind of rush if you both scout and do not overdo it - it beat Niklas' jag rush on the other site's cage match.

Once that is set up, you'll keep using 1 city on settlers, ad nauseam. One of your early core cities will have to pump warriors/archers/swordsmen to keep a good face against barbs and agressive AI's. You'll push settlers out of new, low-shield cities as well as out of your high food openers. Have at least as many worker pumps as settler pumps when you start expanding further. Producing 2 workers per settler is not a luxury.
So, early, you want: 2 settlers every 4 turns, 2 workers every 2 turns, 1 sword every 4, the rest of your empire does either military (if 3+ shields) or settlers (otherwise).

You'll want to get to republic (Monarchy if AW) as soon as you can. Depending on the settings, you'll either want to have early libs or to have a huge amount of swords. Both ways, try to conquer your closest neighbor if it doesn't sound stupid. Meanwhile, your core will start building infra and troops, your peripherals will dish out artillery, extra settlers and workers. 2 workers per city until everything is improved.

On most settings, the real warfare begins at knights. Get knights, kill AI's, grow some specialist farms. If you face a human, pikes, MDI's and trebs are also very good to have in a big stack, hidden at their doorstep.

In the medieval era, capturing land for specialist ICP farms is more important than getting universities. Getting universities is very important if your neighbors want a tech race, so in both cases, use the knights. In an archi map, this could be impossible. Make sure to optimize research.

The next big steps are cavalry, rails and infantry. Whoever gets to each of that first has a big war advantage. Artilleries and infantries are game breaking. Abuse of artillery. The game should generally end there, for either side.