There's no need to read the Poirot books in any particular order.
Agatha Christie has rewritten a few of the early Poirot short stories (see list) from the book Poirot's Early Cases (1923) and The Regatta Mystery and Other Stories (1939) and the posthumous collection While the Light Lasts and Other Stories (1997) into full novels later. Thus, if you read those short story collections, there is a risk that you get spoilers for several novels.
Other than that, the Poirot books sometimes mention earlier stories, but only in minor ways, and they never spoil them. Nor are the earlier books necessary to understand the plot of newer books. At least this is what I believe from reading over a dozen of the 45 Poirot books, so there might be exceptions.
This applies to Curtain too. Indeed, Curtain is the last Poirot story in universe, and Agatha Christie has always intended so. But Curtain makes only minor references to a few of the earlier stories, and is readable independently of those. In particular, Curtain happens in the same location as the very first story The Mysterious Affair at Styles, but apart from Poirot and his companion Hastings, it has entirely new characters, and the mysteries in the two are completely unrelated as well.
The short story collection The Labours of Hercules (1947) has a frame story connecting the short stories in it, so the short stories in any one of the short story collections should be read together in order.
If you are new to Agatha Christie, then I would advise against reading the books in chronological order, because if you give up halfway, then you might miss some of the best books. While certain famous authors like Asimov or Verne have written their best books at the start of their carrier, and then after they became famous, they wrote mostly average quality books with only a few gems, this doesn't seem to be true to Agatha Christie.