One of the reasons it is 'frowned upon' (in my understanding) is that it is a bait and switch--when the dream ends, the story changes to 'real life.'
You can get around that by signaling that this is a dream up front. The dream was as lovely as ever, Neville's arms had drawn her close and jasmine hung heavy in the air...
This is important—the opening of
Rebecca, which Ari cited above, famously does this: “Last night I dreamt I went to Manderley again.” You know right away that you are in a dream—there is no chance of fooling the reader only to “gotcha” them later. I think that is a rather crucial element of opening with a dream sequence. There’s also a lot of subtlety in this one line (though it is followed with a rather lengthy description of the narrator’s dreamland visit to her former home)—there is immediacy in “last night,” and there is intriguing ambiguity in “again” — does it modify “went,” or does it modify “dreamt”? Either way it creates reader interest, because it establishes that Manderley is a place that the narrator has either been to, or dreamt about—or both—before.
In short, it’s a positively masterful opening line, and it shows why people say that even types of openings that are cliche and overdone can be pulled off if done with mastery. (Also
Rebecca was first published in 1935, if memory serves; styles and preferences have changed rather a lot in the intervening near-century.)
At any rate, the problem with cliche and overdone tropes is not that nobody can do them with mastery. Rather it’s that because they are cliche and overdone, when one uses one, one begins with the deck stacked against one. As I said in a recent thread about wake-up opening, the fact that agents and editors see this type of opening frequently enough to complain about its frequency is sufficient to steer me away from it. Even if one can cite dozens of examples of it done well, why should I set out to start my story the way dozens of others start well and hundreds start weakly? Why not instead pick something particular to my story, something that makes my story mine, and start with that? It was an eye-opening way to think about the problem, for me.
OP, you say that dreams are important in your world, which is great—but the reader of the opening doesn’t know that yet; they only know that they’ve been snookered into thinking something was real (within the story) that wasn’t. Can you start somewhere else, and have the dream be present in the POV character’s mind? That will give you a chance to show the dream’s importance without literally starting with the dream itself. There are so many ways to show that a character is a dreamer who lives in a fantasy world (see Shirley Jackson’s
The Haunting of Hill House for an example of a POV character who slips seamlessly into and out of fantasy); you don’t have to literally start with the fantasy itself to show that. (Also, a daydream and a sleeping dream are not in any way the same thing.) It’s something to think about, anyway.
