At this rate, however, world domination by day 500 definitely can't happen. Swadia has a never-ending horde of lords, and I only have 5 vassals backing me up. i have a reserve of around 900 soldiers, but during a very unfortunate fight last night I lost around 120 Arbalestiers, which were crucial for sieging.
I definitely learned some things about how it COULD work. Some things:
1) Quests are largely a waste of time. Especially any quest that takes you out of actively pursuing your domination for more than a few game-hours. Rely on quick quests and donations to build up rep, or only build up rep at key cities and let the rest go to your generals or just be unclaimed.
2) You will want a war chest of at least 200k before you start conquering, and you will want dyeworks in virtually every city
3) Owning a city by day 150 is not only reasonable, but quite easy - realistically you need to be much more aggressive. I would shoot for owning a city by day 75.
4) The sarranids get torn to shreds by heavy cavalry, and are the easiest faction to conquer.
5) Don't go after cities that aren't sure things. I spent nearly 90 game days "preparing" to take Jelkala - it wasn't worth it in the end, I should have focused my efforts elsewhere.
6) There's no need for you to hold on to a lot of territory. Pick a city and pick a castle near that city - the rest, let it be half unowned and half given to your generals. The rents you collect are really nothing to write home about.
7) Always, always always be aggressive about looting and selling your loot. Even after rents and all my dyeworks, I still lost anywhere from 15k to 40k a month to wages - and this was still not enough to keep many of my outlying areas from being sieged

Don't put your prisoners in cities. Keep a castle for yourself and stick them in there. Otherwise you'll be challenged to duels CONSTANTLY and have really dismal honor / dismal reputation with lords as a result.
9) Assassinations are very, very harmful. Give yourself at least 10 STR so you can wear great helms / sarranid elite armors / etc. You might even want to go up to 12 STR to don some heavy plate. Pick up some ivory arrows and a decent bow as early as you can. Do not let yourself get assassinated!
For reference, I'm currently level 31 and my stat distribution is 10 STR, 18 AGI, 30 INT, 12 CHA. I started with 9/15/9/9, raised AGI first, then STR, then INT, CHA last. I felt this was ideal as it let me pick up better gear earlier on. My skills are 3 Ironflesh, 4 power draw, 10 pathfinding/spotting/training, 4 leadership, 2 prisoner management, then a bunch of misc. If I had to change, I might go to 12 STR first instead of 12, so I could wear Rhodok plate and get another point of iron flesh - mostly to protect against assassinations.