Beginner level player: I managed to move from lowly Duke to King of Wales and Ireland. Well, how do I proceed from here?

This is a request for guidance on how to take over as Emperor of the British Isles.

Having scoured this subreddit for information, I began a game as the Duke of Gwynedd and worked my way up to King of Wales. Scotland had ruled 7/13 Counties of Ireland until I was recently able to conquer another Dublin during a war of succession or something, when one of the Dukes split off with the Duke of Moray for a bit.

I have made the Kingdom of Ireland and would like to become Emperor of Britain, but I don't really know how to go about that. Right now, half of Ireland is owned by me while the middle is split between England and Scotland, though I don't know how that happened, and the big island is all split up as England seems to have taken much of Scotland but is now in the midst of a big inter-feud for control.

In all of this, I own all but one County in Wales, half of Ireland, and my wife has a Weak Claim on England. Should I press that while England is having a crisis, or should I attempt to take more land via marriages (which I don't think I have a great grasp on)? Any advice would be wonderful.