>>600
Definitely start with The Hobbit first. Then The Lord of the Rings. The Lord of the Rings is a sequel, and though you theoretically can understand it without reading The Hobbit, indeed the movies expected you to understand them without knowing The Hobbit, you're missing out if you go that way. The Hobbit is a lighter read for younger audiences, but it does help to introduce you to the writing style and to the world and characters. It eases you into things. The Lord of the Rings then follows that same progression. It begins with a tone and style much in line with The Hobbit, but becomes something very different by the end. Also, Tolkien seemed to consider it all part of the same story. At the end of The Lord of the Rings, Frodo and Sam discuss the book that began as Bilbo's memoirs, then became Frodo's more scholarly account of "What we did in The War of the Ring." They mention that it's left to Sam to finish the last chapter, and the number given is the number of chapters in the whole book, if you add up all the chapters in The Hobbit and all of the books in The Lord of the Rings. It's one story. You can stop reading after The Hobbit if you want, it has an ending, but The Hobbit is the beginning of The Lord of the Rings.
After that, you could bother with things like The Adventures of Tom Bombadil, or Bilbo's Last Song, but those are collections of poetry, and while they are supposed to be poems in-universe, written by characters from the novels, it's not like they're essential reading. They're very short, either way.
The Silmarillion is a narrative, and a prequel, but should most definitely be read after The Lord of the Rings. I mentioned that the style changes to one that is much more adult and difficult over the course of The Lord of the Rings. That trend continues into The Silmarillion. The Hobbit and The Lord of the Rings are "written by" (in-universe) hobbits, simple people who speak simply and love simple poems and songs. The Silmarillion is written by elves, stuck up bastards who love being fancy for the sake of it. All the things people say are complicated in The Lord of the Rings, like the use of many different words from different made up languages, the many different names from made up languages, some of which sound similar to each other (Sauron and Saruman), the zillions of characters you're expected to keep track of, all of these things are multiplied in The Silmarillion. Also, while there ultimately does pay off an overarching narrative, really it's a collection of short stories presented in chronological order. But you don't wanna take a break reading between stories, because you might lose the thread of the overarching plot, which is easy when you're expected to remember all these elvish names that might not be mentioned for hundreds of pages.
However, if you read The Lord of the Rings before The Silmarillion, you'll already be at least somewhat familiar with many of the main characters, though they're only mentioned a few times here and there in The Lord of the Rings. You'll be somewhat familiar with elvish languages. Also, you'll be more interested because you're learning about these things that are treated as distant and mysterious in The Lord of the Rings. The themes that are in the previous books are expanded upon to much deeper degree here. Though Tolkien started writing this earlier than The Hobbit, he never finished it before he died, and as he got older he got more and more into his own head, and let himself explore the ideas and themes with much more depth. So all the things I'm saying make The Silmarillion difficult do make it better, but you should be primed for it first. The Hobbit and The Lord of the Rings do refer to things from The Silmarillion, but only as wise mysterious characters talk about them, and the protagonists don't understand, so it's okay if you don't understand, and you and the protagonists just pick up little bits along the way. Then you can read the full book later and learn more. The Silmarillion doesn't expect you to know The Lord of the Rings, but if you do, you'll enjoy it more as you find out more about characters you heard mentioned but didn't learn much about.
There are then tons of other things Tolkien's son published after his death, most of which seem like notes and rough drafts, but a few which seem like narratives, but I still don't know where to start with those, because really I only want to read the narratives, not the notes.
>tl;dr: The Hobbit, The Lord of the Rings, The Silmarillion, in that order. You can read The Adventures of Tom Bombadil and Bilbo's Last Song before The Silmarillion if you want. They're just short little in-universe poems.