I think I had pretty good taste for my budget, looking back on things. Nothing that's gone up much in value, but I'm happy with what I've got.
I've always liked lobby cards, but the one buying choice I would do differently, is I would not buy single cards to try to cobble together a set. Yes, it was kind of a "thrill of the hunt" thing that I went through, and you never knew if you'd see another card again in a certain condition... But in hindsight, I have since seen all of these lobby cards sell as complete sets for way less than what I paid in total for my sets. I can't complain too much, though. Those were fun days, ordering a Vincent Price lobby card in "Excellent condition," and opening it up to find a decently NM card. I used to dream of framing them all, but darned if I ever find the wall space. I keep them nicely organized in albums, though, that are fun to flip through from time to time.
Like others, my biggest regret is selling some really awesome stuff that I haven't seen since (like a couple original color fotobustes from the original Italian release of the Claude Rains "Phantom of the Opera"). Made a small profit then, would've made a huge profit if I kept them today. But I always had fun doing a bit of buying AND selling. Could've done worse.