I’m one of those heathens that read through for the first time in publication order. The ancient civilization side trips were a bit disorienting at first but I managed.
Ok but where do I start?
You can do whatever I think, either read them by series (rincewind, witches, city guard, etc.) or by publishing order, starting with the colour of magic.
Holy crap the Watch series are so good.
It’s good right up until the last two books or so (thinking specifically of Snuff, but also Raising Steam here), where Vimes becomes a complete parody of himself, and there is also a large drop in quality.
Maybe Pratchett’s disease had something to do with it.
I was the weird one and started with The Color of Magic and didn’t regret it. Weird Pratchett advised to skip 2 of his own books.
Don’t sleep on Small Gods, it’s incredibly good.