There's no definite answer. It varies a lot. And which editions are the most worth having varies a lot. Lemme pick one as an example. (Reddit won't let me tell you what the book is). This search site lets you sort books by asking price, either cheapest or most expensive first. A first edition will often be at the pricy end.

https://www.addall.com/SuperRare/UsedPage.html?id=221018064217113313

Other search sites let you specify if you want a first edition.

Remember that most books never get a second edition because they flop. That doesn't make them valuable to anybody.