Well I have never made my own kingdom, simply because that aspect of the game/mods has never appealed to me. So I really can't offer any advice about that. Actually I've spent most of my time as an enlisted man ever since Brytenwalda has incorporated Freelancer into the mod. Though I eventually end up becoming a lord to the kingdom I enlisted into.
From what I've heard from other people you will want at the very least a city and one to two castles-as well as a high right to rule before starting your own kingdom. I guess having other lords like you and a few companions would only improve the situation.
I have only played a little in and around Ireland so I'm not the best person to offer advice about the best path to take. I've spent almost all of my time around the Jutes, Saxons, and Britons. I typically find it just easier to enlist into a lords/kings army to begin with. Usually with a faction I plan on joining and one that won't get owned right away. I usually stick with this for a while until I reach the top tier of the troop tree (this is usually a elite infantry or in some factions cavalry) - thus allowing me to net some pretty decent gear, experience, etc. I also take breaks as a soldier, making good use of the whole 2 week vacation you can request from your commanding lord/king. I use this time to build up relations with the other lords-this is easy to do simply by recruiting a good many soldiers into your own army. Track down the lord in question (but only when he is outside a castle/town) and give him troops. Depending on how many and the quality of troops his disposition toward you will go up a little or a lot.
This is also a good time to find bards to teach you a few poems for when/if you decide to court/marry a lady. Also if you have a decent amount of money you may want to invest into buying land at a town your faction owns as well as maybe buying/building a business in said town. Also you should think about spending some money to increase your fame (via a bard in a town castle) or your honor (via a priest in a town castle).
Of course if you have the money you could also build yourself a lair and between breaks start stocking it with a few soldiers. But since you are a enlisted man your income will be limited to the wages you make as a soldier, any businesses/land you own, and by loot you obtain from battles.
Now, after I have fought a while, saved up some money, gotten on good terms with the faction king/lords, etc I then decide if I'm ready to join as a lord. If you have been increasing relations with lords/kings and using money to up your renown/honor here and there simple talk to your commander and choose to leave. Then simply find the King and become a vassal.
Here is the good news. If you have taken some time (as an enlisted soldier) to do all these things you should have decent renown, honor, money, relations, etc you should be in a good position to request a certain town/castle/etc after it is conquered. Meaning you can talk to your new found lords who you have befriended to support you in receiving said new town/castle/etc.
I'm not sure how this would play out in certain regions/factions on the map but during my service with Cantware I managed this fairly easy. After 90 or so days of serving I had plenty of money, some troops, friendships abound and once I joined I was given a meager village but as soon as the faction took over Seal-sy I requested/got support from the King/other lords and received my just due. From there is only got easier.
That was my experience anyway and please don't take this jumbled garb of text as a sure fire way to playing the game. Just play it the way you want, have fun doing it, and work out your own methods.
