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I wouldn't bother with much of the "optional stuff" until you've read the main trilogy twice. Silmarillion is a good next step.
Unfinished Tales is just that - a lot of "unfinished" and often contradictory stories. Something people new to the space don't quite understand is that a LOT of the works in UT/HoME are not actual complete, fleshed out stories - but notes on directions that Tolkien jotted down, him starting to take characaters/stories in certain places, changing his mind and then creating another version. But it's all recorded, so we read and study them all.
I would suggest avoiding those two for now as they might confuse you until you fully grasp the main stories. A lot of these subs also struggle with that when regarding the show, because they believe there is an actual "canon" that was broken having only read, say, the Silmarillion, without reading more of Tolkien's ideas for the second age.
My suggestion would be to read
Don't sleep on the readers companion; make sure it's the one by H&S. It's AMAZING, and it complements a second re-read so well.
Hammond and Scull are well-regarded. Generally, though, the best writers tend to focus on scholarship rather than general reference. There aren't a lot of good books of that type for Tolkien, probably because to go into sufficient depth, you have to make your reader spend just as much time on your book as if they were just reading Tolkien's books themselves. The other end of the spectrum is stuff like "Lord of the Rings for Dummies," which, while more reliable than Day, is pretty shallow, and in between, there's just a big gap.
That's how Day managed to make such bank on his high-visibility, low-information book series. The people who were already familiar with JRRT indepth instantly spotted the insufferably poor quality, but newcomers to the fandom, if they were looking for an abridged catalog of "the lore," thought they were finding a great prize that would help them "get up to speed." His books look very tempting if you don't know what you're getting.
He takes quite an authoritative tone in them, too, with the result that we regularly get newcomers posting here attempting to show off some bit of knowledge, only to be quickly told that "that's wrong, and it sounds like something you'd read in David Day," and that's when they find they have a lot of learning to unlearn.
You dodged a bullet.
See the "look inside" here. It looks extremely dry to me personally. Then again I could never get into The History of Middle Earth, so I imagine people who do would enjoy the Reader's Companion.
The Lord of the Rings: A Reader's Companion https://www.amazon.com/dp/0618642676/ref=cm_sw_r_cp_api_glt_fabc_HPGVQB3QXCR49G5HXMFZ
Thank you (-: But Again about a guide, do you know anything about this one? https://www.amazon.com/Lord-Rings-Readers-Companion/dp/0618642676
I'll keep looking. Maybe if someone has an actual copy of Hammond and Scull's LotR's Reader's Guide they can swoop in to save the day.
I can't suggest a nice set but I noticed that you had missed out the Readers Companion!