I can’t, however, wholeheartedly recommend it, since you said you were just finishing up your first playthrough on normal, and relative to that, this build is substantially further out in terms of hours played. While the key item set here is target farmable (IIRC each of the four pieces has something like a 5% drop chance from a corresponding chest at the end of a different roguelike dungeon), what this means in practice is that first, you need a build that can comfortably farm these dungeons, and then you need to do an average of 20 successful runs per dungeon to get the full set.
If you’re looking for something more immediate, I suggest you take a look at this beginner build collection put together by @Nery
with links to beginner builds from other users near the end of the first post there. What you’ll find with these beginner guides are builds that can largely be assembled with faction gear, craftable, and easily farmable items as well as leveling guides and other helpful tips. While these builds won’t, in general, perform as well as the forum builds you see stuffed to the brim with legendary items, they should be both capable of the early endgame farming you need to start assembling your collection of gear and suitable stepping stones to higher-end builds later down the road as you get more gear to upgrade them (or even respec them to entirely different playstyles once you have the necessary items).
Given what you’ve referenced in your post, I assume you’ve probably taken a look at at least some beginner content, so I apologize if I’m presenting something redundant with what you’ve already encountered. I also don’t mean to respond to what is clearly a very specific request with a broad answer, but rather to supplement an answer with resources designed to get you SOMETHING up and running in Ultimate difficulty so that you can begin to collect a variety of endgame gear for other builds.
As far as oathkeepers are concerned, there should be a couple to peruse in the beginner guides as well, but perhaps others can better entertain the specifics of your request.
Lastly, welcome to the forums! I’m happy to hear you’re enjoying this great game!
Thank you guys! Awesome suggestions if anyone has anything more to add please do! This game is so big with so many different builds that suggestions to narrow it down from experienced players are worth a lot to me.