Inner Turmoil achievement run as The Isles:
Allies: Portugal, Castile
Junior Partner: Burgundy
Turns out it's better if England doesn't rival Scotland if you want them to support your independence, because they desire your capital and are hostile if they rival your overlord.
England and Denmark both supported my independence straight off the bat in Dec 1444. I gave France Maine and Bordeaux from my English ally to get them out of the war ASAP. Denmark sieged down the Dumfries fort for me which was nice so I took all the cores of Gaeldom plus Ayrshire and Dumrfries along with my independence in 1446, while giving Lothian to England to keep them only slightly upset with me and still willing to be my ally. I ditched Denmark. I immediately released Gaeldom as a vassal because I needed to stab up from -3 and couldn't afford to core those provinces.
Started improving relations with Castile, because the plan was to invade one of the north African subjects of Morocco with their support once I had the 3rd Exploration idea and the coring range to reach them. This never eventuated, although I did go Exploration-Expansion with my idea sets. Castile ended up losing their first war to Granada and gave up three provinces to Granada. Portugal then defeated Granada and took a few Castilian cores in the peace deal, while Aragon sniped one from Granada to finish them off.
I forced spawned Renaissance in Ayrshire through devving, using mostly admin and mil points.
During the 1460s Burgundy declared war on England while Portugal was busy and took Calais and forced England to release Meath and give up three vassals it had acquired in Ireland. I was in this war too but didn't get impacted by the peace deal. Also during this time, France declared on England for its remaining cores and again I was included in the war but separate peaced out in exchange for breaking all deals with England.
In the 5 years of peace with England, I annexed Gaeldom and got claims on Meath, Ulster and Leinster (former English vassals) all of which had no allies. I annexed Meath and made Ulster and Leinster my vassals. This allowed me to build up my force limit to 16 which was about the same size as England's standing army. Portugal was in debt and dishonored it's alliance with England when I attacked them for Lothian, a couple of other English provinces in Scotland and Ireland, humiliation and about 500 ducats.
After mopping up Ireland it was time to start colonising. With the 3rd idea from Exploration (+50%) plus a Colonial Range advisor (+20%) plus 10% from the decision that is enabled from the Burgher new world charter estate privilege I was able to reach mainland Canada for my first colonial province. I took a Burgher diet mission to colonise Greenland for faster colonisation as my second colony, my third was in South Carolina and my fourth was Arguin in North Africa.
While I was at war with the native Americans in Florida and Jolof in West Africa, I got Burgundy as a junior partner. They had been allied to Aragon but Aragon fell under PU to Castile, and Burgundy was rivalled to both Austria and France so they chose me.
Austria declared war on me for the Lowlands, but with Spain and Portugal's help I was able to white peace them out just as I conquered my 20th non-island province in North America.