Guide to Ireland
As Petty King Murchad start with Overseer as this gives Stewardship, Control, and Tax benefits. I like the Authority focus for the Control Growth bonus.
At the start, I only find a wife for my main (Petty King Murchad), and look for a high Stewardship with Rank 4 (Midas Touched), plus a good collection of other stats and good personality traits. If you can find someone with these plus a good congenital (inheritable trait), it’s a bonus!
Sway your Bishop first if he doesn’t endorse you. Also I like to then sway the Spymaster as I you don’t want your Spymaster working against you!
Desmond is your first target. But I wait until I build two Bowman regiments so to win easily and have enough men to siege.
While you wait for the 150 gold, set your Chancellor to Domestic Affairs, and your Steward to Collect Taxes. Have your wife set on Manage Domain for the extra income.
Make sure to set your Knights on Force or Forbid. For example set your Heir and other key people on Forbid, unless you want your Heir to get killed off if someone next in line of succession is better.
Hire a Court Physician from your Courtiers with a high Learning skill. Don’t overspend at the start on a Physician.
A good way to recruit really good people is to have your unmarried female Courtiers marry matrimonially, and to marry someone with the high skill you need. Remember to invite to court unmarried female guests (when cheap) so you can do the above matrimonial marry maneuver.
For my first Lifestyle pick I go with Bellum Justum for cheaper Casus Belli. Then Parthian Tactics for stronger Skirmishers. After these two picks, re-focus to a Stewardship Lifestyle with a Wealth Focus for the +10% income. And go down the Avaricious tree first for the sweet Avaricious trait. Your choice after that.
Focus on gaining hooks if you can with your spymaster on the two vassals with holdings. And Fabricate a claim on the holding you just conquered (Desmond) and the other holding (Ormond) from your other vassal Earl.
Once the claim on Desmond is finished, set your Crown Authority to Limited Crown Authority. Then revoke the Tile of Earldom of Desmond from Earl Muiredach. He will probably reject the ‘Request’ , and you go kill him again.
Once he is in jail, you can re-request he gives up his title to the Earldom of Desmond, and he will now accept! You now have the Earldom of Desmond. Next, do the same process on the Earldom of Ormond and Earl Ragnvald. Now you have less people to keep happy (just your Mayors), and no Liberty Revolt risk from your Earls!
The end goal is to consolidate the entire duchy under your rule (except cities and temples, just increase those vassals' opinions you can’t hold those titles).
Now that you have the Petty Kingdom of Munster under full control, start building your castle infrastructure, focusing on generating income. Build new Castles Holdings when you can afford them.
With the gold you're making building up Munster, rinse repeat this strategy for another duchy until you hit your domain limit. Only then start relying on vassals (preferably your dynasty).
Start swaying your Council or Mayors as you see fit. Keep recruiting better people for your council using the matrimonial marriage strategy.
Try to ensure you get the best Heir, with the goal being high Stewardship with Rank 4 (Midas Touched), plus a good collection of other stats and good personality traits.
Your third child can also go down the Stewardship Lifestyle tree. Or if you want to change it up, have your third or fourth child be a Learning focused child, and go down the Learning Lifestyle, with a Scholarship focus and go down the middle Scholar tree, and then switch to a Stewardship Lifestyle for the extra income.
Life is so much easier with less people to keep happy, and a flush bank account! All the infrastructure you build up with help make your army a juggernaut. Ireland should be fully yours without having to hire those expensive mercenaries.
Make development a priority, and you should be quite a bit ahead of your neighbours. Your Innovations should also be way ahead if you groomed your 3rd or 4th Heir to be a Learning powerhouse. Luck of the Irish to you.