What is a good civ for a warmongering noob? I've won diplomatic, cultural, and science victories but I always have a really bad military. I'm gonna try for a domination win. (Also don't recommend Rome because I've played the recently)
Either Persians or Egyptians, use their chariot-based (2-move) unique unit for early destruction of your neighbors.
rudimentary "how-to":
Spoiler :
PLay on a map where there will be opponents accessible by land. Use your scout to clear the map near you, and then find the nearest AI (it helps to add some extra opponents, making the avg distance between you and them smaller). Pangea or Inland sea are nice. Research Animal Husbandry first, wheel second. Then you want bronze working after that for whipping and chopping. Find horses. If you need to settle a second city to get the horses, your build order will be something like: worker > warrior (to pop2) > settler. Settle next to the horse, you don't want to have to wait for border expansions by culture. Worker constructs a pasture, and connects with roads to capitol. From there on you build nothing except Immortals or War Chariots. "How many" will be depending on your difficulty level. At say... monarch level... when you have six or seven stacked, move them out and kill someone. Use the whip as much as you can - as fast as it dissipates. And your worker should be chop chop chopping. Note, do NOT stop building Immortals/War charriots. Killing your neighbors is like eating Lay's potato chips, its hard to stop after just one. 
You should be able to conquer the world without having built anything but units (at least on Prince and below). Note, after BW, you might want pottery to keep your economy afloat wit hcottages... but you could also just put the slider at zero and store up cash the rest of the game. BTW: Its easier to keep the economy going if you follow this simple rule: Keep the best, RAZE the rest.

You should be able to conquer the world without having built anything but units (at least on Prince and below). Note, after BW, you might want pottery to keep your economy afloat wit hcottages... but you could also just put the slider at zero and store up cash the rest of the game. BTW: Its easier to keep the economy going if you follow this simple rule: Keep the best, RAZE the rest.