I'd like to throw my support behind a beeline to samurai and then much wailing and smashing of enemies.
It plays right into your civ's strengths; an excellent military. Samurai are incredibly effective from the instant you get them up through musketmen. (str 9 vs str 8.8 and 2 first strikes...and the samurai is 10
cheaper) The archery units (longbows and crossbows) you'll be using to defend your ill-gotten gains are also more effective. All of this means that your military will either be smaller than a typical military in the middle ages or significantly more effective. That saves you
in unit upkeep. Furthermore, the first strikes means your mainline offensive units take less damage, so waste less time healing. If you're doing a lot of fighting, you'll likely have a couple of GG's. Using the first one or two on medic 3 units means you might have a turn, two tops healing after each enemy city before you move on. The extras can go towards MIs, which will make your eventual gunpowder armies simply unfair. Six promotions out of the gate on a rifleman? That's a touch obscene, and easy to get - barracks, MI, vassalage/theocracy. Yeah, yeah, I know running both vassalage and theocracy is lame...but it's so much fun! CG 3, Drill 1, Pinch, Combat 1 riflemen are also almost impossible to displace from cities, and give even artillery and infantry a run for their money. This means you can hang onto your conquered cities for a long time to come.
As far as medieval offenses goes, I'd smash at least one civ, preferably one and a half or two. One and a half means finishing somebody with gunpowder units. Maybe you could kill one with samurai and then build up your cats to move onto the second; if you move quickly enough off your beeline, you might not need cats/trebs to take out one AI, although I don't know how that'll go at Monarch.
By the time you finish your medieval offenses, you should be big and bad, and poised to transition to a building period, defending your territories with ridiculously over-promoted units; both vets and newly built riflemen/grenadiers.
Another option is to take out one civ early in the middle ages; either starting with axemen moving to samurai ASAP, or just samurai, (I'd say samurai) then wounding another civ and vassalizing it. If you vassalize a nice techy AI; Mansa, Liz, Washington, though Gandhi would be best, you can extort techs from them for a long time to come. That can help you get out of the tech deficit such a large military effort can get you in.
On second thought, take out the peaceful civ first, and vasselize them. If you take the feudalism route to civil service, that gives you very nice options for putting together your army. Since you wont have taken over too many of their cities, you won't need courthouses as badly. Plus, you can backfill CoL while smashing faces. Then get the vassal civ in on your second offensive; against another nearby neighbor, to get some shared military struggle bonuses going with your vassal. I find happy vassals are much more productive than angry vassals, and the keys to that are sharing a religion and sharing wars. Unfortunately, I can't think of any civs who have really high shared religion modifiers and are also relatively tech/trade emphasized. Brennus I know has an amazingly high shared religion modifier, (he was friendly with me while I was crushing his empire; +7 shared religion, which was really nice post-vassalization) but I don't recall how crazy he is about techs and trading.
This strategy also has the bonus that you can probably extort construction from the peaceful civ you vasselize, giving you the tools for your second offensive, and the lack of catapults wont hurt as much since a more peace-mongering opponent will be easier to knock over in the early game (Gandhi builds a big army in the modern age, sure...but early? not so much).
Relatively early offenses also have the benefit that they'll help you deal with the whims of the map generator. You'll want to do some serious exploring to find prime victims and determine what kind of map you're on, and then the war gives you a chance to grab weird sites fractal has set up which can be advantageous.
A couple of key concerns.
First, make absolutely sure you get iron. Samurai are incredible and you want them. If you only have copper, find someone with iron and destroy them. Salt their land. Crush their homes. Level their temples. Et cetera.
Second, don't worry too much if your economy looks like it will tank. Remember back on ALC 10 when everyone was wailing over the GNP graph? GNP only gives commerce. It doesn't pay any attention to beakers brought in from, say, specialists. Which are really nice. An SE, for instance, might make a lot of sense (more on that later).
Third, don't get distracted. ALC 11 you got a bit distracted about war what with the NCs sucking and all. Samurai are amazing. You want them. Don't forget it. As tasty as the great library is, or other cool things on that tech tree, I think you've gotten a little dependent on them. Try something new! When was the last time you went for CS via feudalism? Or, really, saw anyone else do that? Remember; things like the GL, or even liberalism, are not necessary for victory. They're sure nice, but you can get by without them. If you want them, make sure the opportunity cost is worth it.
So, my last comment is about the idea of a SE. You may not be philosophical, but SE can still be really cool. It also means you can run a lower science slider and still get techs decently, (bulb and trade; higher diff means more AI techs for trading) which supports your warmongery ways. I think you should go for an SE for a couple of reasons. It gets more effective at higher difficulties, primarily because of AI trading, so as you move up, I'd try to get used to it. (I shouldn't talk too much about that, though, as I primarily play noble & prince) Second, SE means you don't have to fuss as much about your lack of economic civ traits. Third, it's more flexible with regards to whipping, which also dovetails with a military offense. Fourth, it means you can grab one or two good GP farms, then focus the rest of your empire on other (military) concerns, which also has synergy with warmongeryness.
The only thing I'd watch out for with the SE is the tendency to go the upper tech path for philosophy for pacifism. I'm not worried about running pacifism; I'm worried about getting distracted from samurai. GET SAMURAI FIRST. At the same time, though, I don't think pacifism will hurt you as much as it normally would. The big cost is a large military. Sure, you're going to want a big military, but it'll be okay. Two reasons. First, you'll have a smaller military than most for it's strength (not power, as promos don't count there) since your units get so many promotions and are so nice and smashy. Second, conquest earns you cash as you conquer cities. This can be used in the short run to pay off the city maintenance and the pacifism upkeep. Pacifism's strength is short-ish bursts to grab a couple of quick GPs, and this again has synergy with the quick bursts of war cash. (also if you extort peace from the civ, that can be sweet)
An interesting diplomatic trick could be multiple peace settlements with your second opponent. It'll get you more cash in peace settlements, and more shared military struggle bonuses. If you're planning on exterminating the civ, then the diplo penalties won't be too bad so long as you aren't planning on being friends with any of the victim's friends.
Anyways, that's the long, really rambly way that I say, "Crush, maim, destroy!"
C'mon! You know you want another conquest victory, right? And if you're feeling pansy-enough to go for a space race victory, you can use shale plants to get some extra boosts in that direction. All your traits point towards early warmongering and later building. Sure you have those tasty gunpowder units, but they can just be used for a second or third batch of warmongeryness. As if that's a bad thing!
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