I needed a set of core rulebooks (to play D&D), but I got those in the late 80's. Everything since then has been 'want'. I am (potentially) in the market for an updated set of books, as some of the flaws of 5e have become onerous. But I don't need that. And, unfortunately, it very much looks like WotC are busy 'fixing' things that really didn't need it and failing to fix things that do. But we'll see.
As for expansions of various sorts: it took me far too long to learn this, but most of them actively make the game worse. That has been true of every edition of every RPG I've played. I'd much rather they focused on adventures and settings - even if most of them aren't particularly good either, at least they're easier to fix and/or ignore.