Because it’s hard for a new player to get over the collection curve and get a couple 1000 dust, I would recommend disenchanting some epics and rares you won’t use.
In the spreadsheet, I’d recommend disenchanting cards in the Trash category, and some in the Niche/Casual category, though some are good for a new player to use while you build up your collection.
I’d advise against disenchanting Legendaries, especially from the newest sets. From the older sets, maybe. There is always a small risk that you disenchant a legendary and it becomes useful months later. But if we take a historical example, many legendaries from Rise of Shadows have just fallen off the curve of playability, in Standard at least. In Wild you could make some work.