Afraid I don't have any vids, mainly just played 10ish hours couple of years ago, then got interested early this year and played for 500 more
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I do have some tips how to make it little less overwhelming, though:
Ireland the start you want. Personally, I always play from 769 start, but it might be better from other starts. You can really pick any of the counts there, it doesn't make much difference.
Your character has bunch of stats. The only one that really matters early is martial. Not only does it make your leader much better commander, it also affects how many troops you can raise from your levy.
By default your starting inheritance law is gavelkind, which kinda sucks. Once you die, all your land is split among all your kids. As a result, you want only one kid, which is very risky or alternatively you should switch the inheritance law to something else. Fortunately Irish have access to unique inheritance law, Tanistry, which let's you vote from among all your dynasty members to pick your heir once you die. This is great, since it not only prevents game overs but also let's you skip your drooling imbecile of a son and instead nominate your genius nephew.
There are 3 ways to expand in the game:
1) Regular conquest war like in other PDX titles. You can use your chancellor to fabricate claim on a province, or you can use some other Casus Belli. (Irish start as tribal, so they get very strong Subjugation casus belli they can use once per ruler.)
2) Marriage. Your dynasty is denoted by a red blooddrop on the top of the porttrait. By default, kids are always of the father's dynasty, but if a character is irrelevant OR in your court, they will accept matrilinear marriage, where the kids are of the mother's dynasty. The plan here is to find some distant heir to a throne, matrilinearilly marry him to your dynasty (for example, your daughter), then help him ascend to the throne. This can be done either by murdering everyone who is before him in the line of succession via espionage or...
3) Pressing other people's claims. In CK2, it is hard for your character to have claim to many places. However, ton of random cousins and nephews will have claims to who know what duchies and counties. If they are in your court, you can press their claims, and once you win the war, they get the title. If the character is unlanded, he will become independent, but if you make him your vassal first by giving him some minor title, he will stay as your vassal once you win the war.
The provinces that are directly under your control (demesne) are the most useful - for others you will only get portion of income and troops depending on the mood of the vassal. Your first long-term goal should be to find couple of weak neighbors and fabricate claims on them and conquer them for yourself. You really want to conquer enough land so that you can create a duchy, since it unlocks bunch of new stuff, like conquering the rest of the duchy. Once you are a duke, you should fairly easily be able to conquer most of the Ireland and become a king. From there it is up to you if you want to continue this tutorial game and conquer rest of England or play something else like the Norse and reform the germanic faith.