Like a lot of others here, I collected for my childhood and teen years, and then took a decades-long break. In my late 40s, got re-engaged with the hobby by doing the only reasonable thing -- buying a small boatload of cards in bulk and sorting through them. Sport by sport, year by year. It gave me a pretty good sense for what I'd missed & what I like.
The answer turned out to be a little bit of everything, and especially 70s-90s basketball. Also parallel sets in particular, even though I thought they were gimmicky back when they started to show up way back. (Funny how that works out.)
This site's a great resource -- looking forward to participating in & supporting it.
Update 01/07/24: trading off for the time being...need that slice of time for other things.