I played the original Deus Ex around 10 years ago. Once you accept the aged visual side of it, the world, characters and plot can easily immerse you till the end. I’d say play the original (maybe with some modern visual mods), then skip to Human Revolution, then Mankind Divided.
I didn’t bother with Invisible War and The Fall. I tried them for a moment, but the bugs and clunkiness put me off.
There’s also Deus Ex Go, a mobile game that’s actually a really good puzzle with fantastic music.