This should be someone worthy of being a vassal. Once you have trebs you need alot and should start thinking about a target. Trebs you want attacking cities, catapults are more for defense but you can use them for offense as well, just give them city raider instead. Makes it impossible to destroy the enemy stack. Dont leave the forests next to your cities. Makes it possible to destroy 75 troops with just 40. When the large stacks come now you just hit them with a few catapults to weaken them, and clean up with your other troops. You use them for defense when the enemy comes. Have your production city start building catapults.
Then either tech or trade for construction and get catapults. By now others should have mathematics, trade for it. Settle the great scientists in your best science cities when you get them. Once you get a library in your capitol, turn two citizens into scientists, between that and the great library, that's 4 scientists in your capitol. Go for the boosted great people wonder and the great library in the capitol. Once you get currency go for aesthetics and literature. Currency fixes your economy and lets you grow beyond 4-5 cities. Start growing your cities tall and then start teching currency. If you can get the oracle and don't have stone to get the pyramids then I would grab monarchy with it and trade it for alphabet once another civs got it. For techs obviously bronze working, pottery and writing. Once a second city has a library with good production, give it a barracks, have it do the same. Build a barracks in your military city and load the queue with axemen. Your capital you grow as tall as possible and churn out great people and wonders with. (Stonehenge is awesome) It should be your highest production city that's NOT your capital. It needs a granary and a barracks, nothing else.
That's 2-3 free cities taken for you and twice as much area to settle. Find your closest neighbor and take him out.
The quecha's are cheap, are available from the first turn and eat through archers. First and foremost, destroying your closest neighbor. You need to be on point in everything that you do. If you really wish to get better then its always a good idea to watch a few lets plays. No strategy is perfect but hopefully this helps. This is a short guide I wrote up awhile ago. If you are having trouble on warlord then you should watch some lets plays on youtube. Mostly immortal because deity is a real pain.